Aqueous pigment dispersion and aqueous ink

ABSTRACT

The present invention provides an aqueous pigment dispersion including a pigment, an anionic group-containing organic polymer compound, and bio-nanofibers having an average diameter of 1 nm or more and 100 nm or less and an aspect ratio of 100 or more, and also provides an aqueous ink using the aqueous pigment dispersion. The bio-nanofibers are preferably cellulose nanofibers or chitosan nanofibers. The anionic group-containing organic polymer compound is preferably at least one selected from the group consisting of acrylic resins having anionic groups, polyurethane resins having anionic groups, and polysaccharide derivatives having anionic groups.

TECHNICAL FIELD

The present invention relates to an aqueous pigment dispersion or thelike containing bio-nanofibers and a method for producing the same.

BACKGROUND ART

In recent years, an aqueous ink composition (may be referred to as an“aqueous ink” hereinafter) has taken the place of an organicsolvent-based ink in a wide range of fields because of its safety andlittle environmental load, and particularly an odorless aqueous ink hasbecome essential as an ink which can be used even in a closed space suchas an office or the like.

The aqueous ink is applied to various printing methods such as an offsetprinting method, a gravure printing method, an ink jet recording method,and the like. In particular, the ink jet recording method is capable ofon-demand printing and is thus currently often investigated for thepurpose of replacing an electrophotographic (toner) method used inoffices and the like.

The physical properties required for an aqueous ink using an ink jetrecording method include both the color development (optical density)and rubfastness of a formed image. For this requirement, there is knowna two-liquid reaction system using an image forming ink and a fixing ink(also referred to as a “treatment agent”) (for example, refer to PatentLiteratures 1 to 3). However, in the case of the two-liquid reactionsystem, printing is actually performed in two steps using the imageforming ink and the fixing ink, and thus it is difficult to realizehigh-speed printing at a level equal or higher than theelectrophotographic (toner) method.

On the other hand, bio-nanofibers are produced by uniformly refining(forming nanofibers) cellulose or chitin/chitosan at a nano-level and,in an industrial application, bio-nanofibers are known to be added forthe purpose of improving the drying properties and toughness of coatingfilms by imparting thixotropic viscosity to aqueous emulsioncompositions for coat bonding and filling (for example, refer to PatentLiterature 4), and added to a pigment composition for the purpose ofimparting good rheology characteristics (for example, refer to PatentLiterature 5). However, there has not been known an example of use forthe purpose of improving the optical density and rubfastness of anaqueous ink.

An aqueous ink for writing implements is known, in which an aqueous inkis mixed with modified cellulose nanofibers characterized by a complexstructure in order to secure excellent dispersion stability even of acoloring agent with high specific gravity (for example, refer to PatentLiterature 6). The modified cellulose nanofibers described in PatentLiterature 6 have a predetermined cellulose crystal structure and arerequired to be subjected to reduction reaction to adjust a content ofcarboxyl groups and a total content of aldehyde groups and ketone groupsafter selective oxidation of hydroxyl groups at specified positions in acellulose molecule. Therefore, there is the problem of high cost and alarge chemical limit of ink composition design.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2013-35227

PTL 2: Japanese Unexamined Patent Application Publication No. 2013-35226

PTL 3: Japanese Unexamined Patent Application Publication No.2011-140213

PTL 4: Japanese Unexamined Patent Application Publication No. 10-95922

PTL 5: Japanese Unexamined Patent Application Publication (Translationof PCT Application) No. 2013-527876

PTL 6: Japanese Unexamined Patent Application Publication No.2013-181167

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide an aqueous pigmentdispersion being excellent in optical density and rubfastness of aresultant image and provide an aqueous ink.

Solution to Problem

As a result of earnest research, the inventors found that the problemsdescribed above can be solved by an aqueous pigment dispersion and anaqueous ink each containing, as essential components, bio-nanofibershaving a specified average particle diameter and aspect ratio and ananionic group-containing organic polymer compound functioning as apigment dispersant and a binder.

That is, the present invention provides an aqueous pigment dispersioncontaining at least a pigment, an anionic group-containing organicpolymer compound, and bio-nanofibers having an average diameter (fiberdiameter) of 1 nm or more and 100 nm or less and an aspect ratio of 100or more, and also provides an aqueous ink using the aqueous pigmentdispersion.

Further, present invention provides a method for producing the aqueouspigment dispersion and the aqueous ink.

Advantageous Effects of Invention

According to the present invention, it is possible to provide an aqueouspigment dispersion being excellent in optical density and rubfastness ofa resultant image and to provide an aqueous ink using the aqueouspigment dispersion.

DESCRIPTION OF EMBODIMENTS

(Pigment)

A pigment used in the present invention is at least one pigment selectedfrom known common organic pigments or inorganic pigments. Also, thepresent invention can use either an untreated pigment or a treatedpigment. The treated pigment includes a so-called self-dispersion typepigment. This is because the self-dispersion type pigment is producedby, for example, bonding (grafting) hydrophilic groups on the surfacesof a pigment through physical treatment or chemical treatment of thepigment.

The self-dispersion type pigment represents a pigment which can bedispersed or dissolved in an aqueous medium without a dispersant. Theexpression “dispersed or dissolved in an aqueous medium without adispersant” represents a state of being stably present in an aqueousmedium due to hydrophilic groups of the surfaces even without using adispersant for dispersing the pigment. The expression “stably present inan aqueous medium” represents being stable (change in pigment particlediameter within +/−30%) for 90 days in water (25° C., solid content of10% by mass) without a dispersant.

The hydrophilic group is preferably one or more hydrophilic groupsselected from the group consisting of —OM, —COOM, —SO₃M, —SO₂M, —SO₂NH₂,—RSO₂M, —PO₃HM, —PO₃M₂, —SO₂NHCOR, —NH₃, and —NR₃, that is, an anionichydrophilic functional group. In these formulae, M each independentlyrepresent a hydrogen atom, an alkali metal, ammonium, a phenyl group ororganic ammonium which may have a substituent. In these formulae, R eachindependently represent an alkyl group having 1 to 12 carbon atoms or anaphthyl group which may have a substituent.

Examples of the self-dispersion type pigment which can be used includepigments treated by methods described in Japanese Unexamined PatentApplication Publication No. 8-3498, Japanese Unexamined PatentApplication Publication (Translation of PCT Application) No.2000-513396, Japanese Unexamined Patent Application Publication(Translation of PCT Application) No. 2008-524400, Japanese UnexaminedPatent Application Publication (Translation of PCT Application) No.2009-515007, Japanese Unexamined Patent Application Publication(Translation of PCT Application) No. 2010-537006, and JapaneseUnexamined Patent Application Publication (Translation of PCTApplication) No. 2012-500866. Either an inorganic pigment or an organicpigment can be used as a raw material of the self-dispersion typepigment.

In printing using plain paper as a recording material, a yellow ink, acyan ink, a magenta ink, a black ink, and the like are used alone or asan ink set of combination of plural inks. Pigments used for these inksare not particularly limited, and pigments used for usual aqueous inkscan be used. Specifically, a known inorganic pigment and organic pigmentwhich can be dispersed in water or a water-soluble organic solvent canbe used. Examples of the inorganic pigment include iron oxide, carbonblack produced by a known method such as a contact method, a furnacemethod, a thermal method, or the like, and the like. Examples of theorganic pigment which can be used include azo pigments (including azolake pigments, insoluble azo pigments, condensed azo pigments, chelateazo pigments, and the like), polycyclic pigments (for example,phthalocyanine pigments, perylene pigments, perinone pigments,anthraquinone pigments, quinacridone pigments, dioxazine pigments,thioindigo pigments, isoindolinone pigments, quinophthalone pigments,and the like), dye chelates (for example, basic dye-type chelates,acidic dye-type chelates, and the like), nitro pigments, nitrosopigments, aniline black, and the like.

Examples of pigments used as carbon black for black inks include No.2300, No. 2200B, No. 900, No. 960, No. 980, No. 33, No. 40, No. 45, No.45L, No. 52, HCF88, MA7, MA8, MA100, and the like, which aremanufactured by Mitsubishi Chemical Corporation); Raven 5750, Raven5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, and the like, whichare manufactured by Columbian Chemicals Company); Regal 400R, Regal330R, Regal 660R, Mogul L, Mogul 700, Monarch 800, Monarch 880, Monarch900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, and thelike, which are manufactured by Cabot Corporation; Color Black FW1, FW2,FW2V, FW18, FW200, S150, S160, and S170, Printex 35, U, V, and 1400U,Special Black 6, 5, 4, and 4A, NIPEX 150, NIPEX 160, NIPEX 170, NIPEX180, and the like, which are manufactured by Degussa Corporation.

Examples of pigments used for yellow inks include C. I. Pigment Yellow1, 2, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114,120, 128, 129, 138, 150, 151, 154, 155, 174, 180, 185, and the like.

Examples of pigments used for magenta inks include C. I. Pigment Red 5,7, 12, 48(Ca), 48(Mn), 57(Ca), 57:1, 112, 122, 123, 146, 168, 176, 184,185, 202, 209, and the like.

Examples of pigments used for cyan inks include C. I. Pigment Blue 1, 2,3, 15, 15:3, 15:4, 16, 22, 60, 63, 66, and the like.

For example, a commercial product may be used as the self-dispersiontype pigment. Examples of the commercial product include “CAB-O-JET200”, “CAB-O-JET 250C”, “CAB-O-JET 260M”, “CAB-O-JET 270Y”, “CAB-O-JET300”, “CAB-O-JET 400”, “CAB-O-JET 450C”, “CAB-O-JET 465M”, and“CAB-O-JET 470Y”, which are manufactured by Cabot Specialty Chemicals,Inc.; “BONJET BLACK CW-2” and “BONJET BLACK CW-3” which are manufacturedby Orient Chemical Industries Co., Ltd.; “LIOJET WD BLACK 002C”manufactured by Toyo Ink Mfg. Co., Ltd., and the like. Also, a pigmentdispersion produced by dispersing the self-dispersion type pigment in anaqueous medium can be used as a commercial product. Examples thereofinclude “SENSIJJET Black SDP100”, “SENSIJJET Black SDP1000”, “SENSIJJETBlack SDP2000”, “Sensijet Ultra Yellow PY74”, “Sensijet Ultra MagentaPR122”, “Sensijet Ultra Cyan PB15:4”, “Sensijet Ultra K”, and the like,which are manufactured by United States, Sensient Colors Inc.

These self-dispersion type pigments may be used alone or in combinationof two or more types.

In particular, when an aqueous ink is used for ink jet, the content(mass basis) of a pigment is preferably 0.5% to 30% and more preferably1.0% to 12% relative to the total amount of the aqueous ink. In order toachieve a sufficient optical density on plain paper, the content is mostpreferably 3% or more and 12% or less. This is because with the contentof less than 3%, a printing density on plain paper cannot be secured,while with the content exceeding 12%, discharge stability of the aqueousink from an ink jet head is degraded due to an increase in ink viscosityor the like.

The particle diameter of the pigment is preferably 1 μm or less and morepreferably 10 nm to 150 nm, and the pigment preferably still morepreferably contains particles of 50 nm to 120 nm.

(Bio-Nanofibers)

The bio-nanofibers used in the present invention represent cellulose orchitin/chitosan uniformly refined (nano-fiberized) at a nano-level.Therefore, the bio-nanofibers may be referred to as “biomass-nanofibers”(reference: Japanese Unexamined Patent Application Publication No.2013-216766, etc.).

Even when the bio-nanofibers used in the present invention containimpurities other than cellulose, chitin, or chitosan, there is noparticular hindrance, but cellulose nanofibers or chitosan nanofibersare preferred.

In the specification, the term “nanofibers” represents a fibrousmaterial having a diameter of 1 nm to 100 nm and an aspect ratio(=length/diameter) of 100 or more. Therefore, the “cellulose nanofibers”represents cellulose fibers having a diameter of 1 nm to 100 nm and anaspect ratio (=length/diameter) of 100 or more.

(Cellulose Nanofibers)

The cellulose nanofibers used in the present invention preferably havean average diameter (may be referred to as “fiber diameter”) of 1 nm to100 nm, more preferably 1 nm to 50 nm, still more preferably 3 nm to 30nm, and even more preferably about 20 nm. The aspect ratio is preferably100 or more, more preferably 100 to 10000, and still more preferably 100to 2000. This is because the range can provide a satisfactory effect atlow cost. The cellulose nanofibers can be used alone or as a mixture oftwo or more types.

The average diameter (short diameter) of the cellulose nanofibers of thepresent invention defines the average diameter and aspect ratio of thecellulose nanofibers under a dry condition. The “aspect ratio” in thepresent invention represents a ratio (average fiber length/averagediameter) of the average fiber length to the average diameter of thecellulose nanofibers. In the present invention, the average diameter andaspect ratio under a dry condition can be measured by a scanningelectron microscope (SEM) or a transmission electron microscope (TEM,with electron staining). For example, a dispersion prepared bydispersing cellulose nanofibers is cast on a substrate and observed withSEM, and diameter and length values of 20 or more fibers per image areread. This is performed for images of at least three regions, which arenot overlapped with each other, to obtain information of the diametersand lengths of at least 30 fibers, preferably 100 fibers. The averagediameter can be calculated from the date of fiber diameters, and theaverage fiber length can be calculated from the date of lengths.However, the aspect ratio under a dry condition may be calculated by amethod other than the method described above unless the value ischanged. In the present invention, the dry condition is a condition inwhich 99% by mass or more of liquid is removed from at least thecellulose nanofibers by a usual known method such as natural drying orreduced-pressure freeze drying.

The cellulose nanofibers used in the present invention can be expressedby the average diameter (short diameter) and aspect ratio calculatedbased on the results of electron microscope observation as describedabove. The cellulose nanofibers can be also expressed by a hydrodynamicparticle diameter using a commercial electrical/optical particlediameter measuring apparatus. The hydrodynamic particle diameter of thecellulose nanofibers used in the present invention can be measured by,for example, using dynamic light scattering Nanotrac particle sizeanalyzer UPA-150EX (manufactured by Nikkiso Co., Ltd.). The hydrodynamicparticle diameter of the cellulose nanofibers described in thespecification corresponds to the average particle diameter of ahydrodynamic equivalent spherical model formed when the cellulosenanofibers are dispersed in a solvent. In principle, a certain volume ofparticles are sorted in order from smaller ones to display a particlediameter distribution. Thus, the mode value corresponds to the maximumvalue of the particle diameter distribution. The 20% particle diameteris the particle diameter when particles at a 20% volume in the particlediameter distribution are sorted, and the 80% particle diameter is theparticle diameter when particles at a 80% volume in the particlediameter distribution are sorted.

The most frequent value (mode value) of the hydrodynamic particlediameter at 0.1% by mass (solvent:water) of the cellulose nanofibersused in the present invention is preferably 100 nm or more and 800 nm orless, more preferably 200 nm or more and 700 nm or less, and still morepreferably 250 nm or more and 650 nm or less. In the hydrodynamicparticle diameter distribution, a value of the 80% particle diameter tothe 20% particle diameter, that is, a value of (80% particlediameter)/(20% particle diameter), is preferably 10 or less, morepreferably 8 or less, and still more preferably 6 or less.

With respect to the cellulose nanofibers used in the present invention,a specific surface area (calculated with ultrasonic dispersiontreatment: 1 minute, sample refractive index: 1.56 to 0.00i, dispersionmedium refractive index: 1.333 to 0.00i) calculated from a particle sizedistribution (volume-based particle diameter distribution) measured by alight scattering method is preferably 800 cm²/cm³ or more and 3000cm²/cm³ or less, more preferably 1000 cm²/cm³ or more and 2800 cm²/cm³or less, and still more preferably 1200 cm²/cm³ or more and 2600 cm²/cm³or less. The specific surface area is a total (cm²) of surface areas ofparticles per unit volume (cm³), but it is a value calculated fromparticle diameter distribution data and thus generally does not agreewith a specific surface area measured based on another measurementprinciple.

In the case of an aqueous ink, the content (mass basis) of the cellulosenanofibers used in the present invention is preferably a cellulosenanofiber/pigment ratio of 1/100 to 1/8, more preferably 1/100 to15/100, still more preferably 1/100 to 14/100, and even more preferably1/100 to 13/15. This is because within the range, color development(optical density) and rubfastness of the formed image reach a desiredlevel without degrading the adaptability for various printing methods.

Thus, when the content of the cellulose nanofibers in an aqueous pigmentdispersion is a specified amount, desired levels of the colordevelopment (optical density) and rubfastness of an image formed withthe aqueous ink can be achieved. Although the mechanism of this has notbeen sufficiently examined, it is supposed as follows.

A glucose unit constituting cellulose takes a chair conformation, andthus hydroxyl groups are arranged in a horizontal direction and only Cand H are arranged in a vertical direction with respect to aglucopyranose ring. Therefore, the vertical direction of cellulose ishydrophobic, while the horizontal direction is hydrophilic. Thistendency is further enhanced by an increase in surface area due tonano-fiberization. Therefore, in the aqueous ink, in a compositematerial of pigment particles composed of the cellulose nanofibers withan anionic group-containing organic polymer compound described below,the interfacial tension between the pigment particles and the anionicgroup-containing organic polymer compound is decreased, and repulsiveforce is imparted to overcome the Van der Waals force between thepigment particles while controlling the charge on the pigment particlesurfaces. It is thus considered that a high degree of balance essentialfor stable dispersion of the pigment can be achieved.

Therefore, even when printing is performed on plain paper containingvarious paper components, the pigment particles can be fixed withoutbeing unnecessarily penetrated into the paper used as an object to beprinted, thereby exhibiting a high optical density, causing no colormixing of color inks adjacent to each other in multicolor-type colorprinting, and causing excellent rubfastness.

In the case of the aqueous ink, particularly for ink jet”, the contentof the cellulose nanofibers is preferably in a range of 0.001% to 3%,more preferably 0.01% to 2%, and still more preferably 0.05% to 1%relative to the total ink mass. This is because with the content of lessthan 0.001%, the optical density and rubfastness cannot be secured,while with the content exceeding 3%, printability is impaired due to anincrease in ink viscosity or the like.

The cellulose nanofibers used in the present invention are notparticularly limited and a commercial product or a product produced by aknown production method can be used. The cellulose nanofibers aregenerally produced by fibrillating or refining a cellulosefiber-containing material by grinding and/or beating using a refiner, ahigh-pressure homogenizer, a medium stirring mill, a millstone, agrinder, or the like, and for example, can be produced by a known methodsuch as a method described in Japanese Unexamined Patent ApplicationPublication No. 2005-42283. Also, microorganisms (for example,acetobacter) can be used for production. Further, a commercial productcan be used. Examples of the cellulose fiber-containing material includeknown materials derived from origins such as plants (for example, wood,bamboo, cotton, jute, kenaf, agricultural residues, cloth, pulp,regenerated pulp, and wastepaper), animals (for example, sea squirt),algaes, microorganisms (for example, acetobacter), microorganismproducts, and the like. In the present invention, any one of thesematerials can be used. Among these, cellulose nanofibers derived fromplants or microorganisms are preferred, and cellulose nanofibers derivedfrom plants are more preferred.

The cellulose nanofibers used in the present invention need not beso-called modified cellulose nanofibers which are chemically modified insome way as described in Japanese Unexamined Patent ApplicationPublication No. 2013-181167 and Japanese Unexamined Patent ApplicationPublication No. 2010-216021, and so-called unmodified cellulosenanofibers produced by, for example, a method described in JapaneseUnexamined Patent Application Publication No. 2011-56456, and anunmodified cellulose nanofiber commercial product can also be used.Examples of the unmodified cellulose nanofiber commercial productinclude bio-nanofiber “BiNFi-s” series of Sugino Machine Limited,“Celish” series of Daicel FineChem Ltd., and “CNF” series of ChuetsuPulp & Paper Co., Ltd. These cellulose nanofibers can be used alone oras a mixture of two or more.

In a ¹³C-NMR chart of the cellulose nanofibers used in the presentinvention, it can be confirmed that a peak at 62 ppm corresponding tothe C6-position of a primary hydroxyl group of a glucose unit ispresent. In the case of modified cellulose nanofibers, for example, whenhydroxyl groups at the C6-positions of glucose units in a cellulosemolecule are partially converted to carboxyl groups by oxidation or thelike, the peak at 62 ppm disappears, and a peak at 178 ppm derived fromcarboxyl groups is present instead.

The cellulose nanofibers used in the present invention are not modifiedby oxidation or the like as described above. Therefore, hydroxyl groupsof cellulose may be slightly substituted with carboxyl groups bytreatment in a process of producing and purifying cellulose nanofibers.However, an amount of substituent generally does not exceed 0.1 mmol/g.

The amount of carboxyl groups can be measured by the following method.First, 60 cm³ of a 0.5% by mass slurry (water dispersion) of cellulosenanofibers is prepared and adjusted to pH 2.5 by adding a 0.1 mol/Laqueous hydrochloric acid solution. Then, electric conductivity ismeasured until the pH becomes 11 by adding dropwise a 0.05 mol/L aqueoussodium hydroxide solution. The amount of carboxyl groups can becalculated by using a formula below from an amount (a) of sodiumhydroxide consumed in a weak acid neutralization step in which theelectric conductivity is gently changed.Carboxyl group amount (mmol/g cellulose nanofibers)=a(cm³)×0.05/cellulose nanofiber mass (g)  [Math. 1]

The thermal decomposition temperature of the cellulose nanofibers usedin the present invention depends on the crystallinity, average degree ofpolymerization, etc. but is generally about 250° C. to 280° C. In thespecification, the thermal decomposition temperature represents atemperature at which the weight starts to decrease due to thermaldecomposition when the temperature is increased from room temperature(temperature rising speed: 5° C./min) by a thermogravimeter-differentialthermal analyzer (TG-DTA). The temperature at which the weight starts todecrease is defined as a temperature at an intersect of a tangent at thetime of large weight decrease and a tangent before weight decrease in agraph in which the weight decrease rate is plotted on the ordinate, andthe temperature is plotted on the abscissa.

The degree of crystallization (ratio of cellulose I-type crystalstructure) of the cellulose nanofibers used in the present invention isnot particularly limited. The degree of crystallization (ratio ofcellulose I-type crystal structure) is determined by X-ray diffraction.For example, the degree of crystallization of type I cellulose can becalculated from X-ray diffraction results by using a method of Segal etal. (L. Segal, J. J. Greely et al, Text. Res. J., 29, 786, 1959) and amethod of Kamide et al. (K. Kamide et al, Polymer J., 17, 909, 1985).That is, the degree of crystallization can be calculated by a formulabelow from the diffraction intensity of a 002 plane at 2θ=22.6° and thediffraction intensity of an amorphous portion at 2θ=18.5° using thediffraction intensities at 2θ=4° to 32° as a baseline in a diffractionchart obtained by X-ray diffraction measurement.χ_(c)=(I _(002c) −I _(a))/I _(002c)×100  [Math. 2]

(In the formula, χ_(c) represents the degree of crystallization of typeI cellulose (%), I_(002c) represents the 002 plane diffraction intensityat 2θ=22.6°, and I_(a) represents the amorphous portion diffractionintensity at 2θ=18.5°.)

The cellulose nanofibers used in the present invention need not bechemically treated by oxidation of cellulose nanofibers and thus neednot be improved in resistance to radical an alkali over a long period oftime, and it is unnecessary to select cellulose with a high degree ofcrystallization of type I cellulose (degree of crystallization of about65% to 85%). That is, the effect of the present invention can beexhibited by using cellulose nanofibers derived from cellulose as astarting material which is produced from wood pulp and which has adegree of crystallization of about 50% to 70% (for example, 55% to 65%).

The crystal form of the cellulose nanofibers used in the presentinvention is not particularly limited. Both Iα- and Iβ-cellulose can bepreferably used as the crystal form of the cellulose nanofibers.Cellulose derived from higher plants such as cotton contains a largeamount of Iβ crystal component, while bacterial cellulose contains alarge amount of Iα crystal component. Cellulose can be properly selectedfrom an economical viewpoint.

(Chitosan Nanofibers)

The chitosan nanofibers used in the present invention preferably have anaverage diameter (referred to as a “fiber diameter”) of 1 to 100 nm,more preferably 1 to 50 nm, still more preferably 3 to 30 nm, and evenmore preferably about 20 nm. The aspect ratio is preferably 100 or more,more preferably 100 to 10,000, and still more preferably 100 to 2000.This is because within the range, a satisfactory effect can be obtainedat low cost. The chitosan nanofibers are used singly, used as a mixtureof two or more types, or used in combination with the cellulosenanofibers.

The average fiber length, average diameter, etc. of the chitosannanofibers of the present invention are defined as the same as theaverage diameter and aspect ratio of the cellulose nanofibers and can becalculated as described above.

The most frequent value (mode value) of the hydrodynamic particlediameter at 0.1% by mass (solvent:water) of the chitosan nanofibers usedin the present invention is preferably 100 nm or more 800 nm or less,more preferably 200 nm or more and 700 nm or less, and still morepreferably 250 nm or more and 650 nm or less. In the hydrodynamicparticle diameter distribution, a ratio value of the 80% particlediameter to the 20% particle diameter, that is, a value of (80% particlediameter)/(20% particle diameter), is preferably 10 or less, morepreferably 8 or less, and still more preferably 6 or less.

With respect to the chitosan nanofibers used in the present invention, aspecific surface area (calculated with ultrasonic dispersion treatment:1 minute, sample refractive index: 1.56 to 0.00i, dispersion mediumrefractive index: 1.333 to 0.00i) calculated from a particle sizedistribution (volume-based particle diameter distribution) measured by alight scattering method is preferably 800 cm²/cm³ or more and 3,000cm²/cm³ or less, more preferably 1,000 cm²/cm³ or more and 2,800 cm²/cm³or less, and still more preferably 1,200 cm²/cm³ or more and 2,600cm²/cm³ or less. The specific surface area is a total (cm²) of surfaceareas of particles per unit volume (cm³), but it is a value calculatedfrom particle diameter distribution data and thus generally does notagree with a specific surface area measured based on another measurementprinciple.

The content (mass basis) of the chitosan nanofibers used in the presentinvention is preferably a chitosan nanofiber/pigment ratio of 1/100 to1/8, more preferably 1/100 to 15/100, still more preferably 1/100 to14/100, and even more preferably 1/100 to 13/100. This is because withinthe range, color development (optical density) and rubfastness of theformed image reach a desired level without degrading the suitability forvarious printing methods.

Thus, when the content of the chitosan nanofibers in the aqueous pigmentdispersion is a specified amount, desired levels of the colordevelopment (optical density) and rubfastness of an image formed withthe aqueous ink can be achieved. The mechanism of this has not beensufficiently examined but is supposed as follows.

Chitosan is an aminosaccharide obtained by deacetylating chitin(β-1,4-poly-N-acetyl-D-glucosamine) extracted from crab and shrimpshells and has a structure in which a hydroxyl group at the C2-positionof cellulose is substituted by an amino group. Conversion (deacetylationreaction) of chitin to chitosan does not completely proceed, andN-acetylglucosamine is often contained in a portion of a sugar chain.When 70% or more of glucosamine residues are deacetylated, chitin isgenerally referred to as “chitosan”. Therefore, the quality of chitosanis shown by a deacetylation rate (may be denoted by “% DA”) measured byNMR spectroscopy, infrared absorption spectroscopy (IR), and a colloidaltitration method.

A glucose unit constituting chitosan takes a chair conformation, andthus hydroxyl groups are arranged in a horizontal direction and only Cand H are arranged in a vertical direction with respect to aglucopyranose ring. Therefore, like in the cellulose nanofibers, thevertical direction of chitosan is hydrophobic, while the horizontaldirection is hydrophilic. This tendency is further enhanced by anincrease in surface area due to nano-fiberization. Therefore, in theaqueous ink, in a composite material of pigment particles composed ofthe chitosan nanofibers with an anionic group-containing organic polymercompound described below, the interfacial tension between the pigmentparticles and the anionic group-containing organic polymer compound isdecreased, and repulsive force is imparted to overcome the Van der Waalsforce between the pigment particles while controlling the charge on thepigment particle surfaces. It is thus considered that a high degree ofbalance essential for stable dispersion of the pigment can be achieved.When a polysaccharide derivative, particularly carboxymethyl celluloseammonium as a polysaccharide derivative, is used as the anionicgroup-containing organic polymer compound, ammonium ion with highbulkiness is considered to contribute to surface potential stabilizationof a complex of the pigment particles composed of chitosan nanofibersand the polysaccharide derivative.

The chitosan nanofibers have the tendency of higher hydrophilicity andcationy than cellulose nanofibers and thus have the tendency to exhibitmore desired physical properties in a magenta pigment- or yellowpigment-dispersed system with high polarity.

Therefore, even when printing is performed on plain paper containingvarious paper components, the pigment particles can be fixed withoutbeing unnecessarily penetrated into the paper used as an object to beprinted, thereby exhibiting a high optical density, causing no colormixing of color inks adjacent to each other in multicolor-type colorprinting, and causing excellent rubfastness.

In the case of an aqueous ink, particularly, for ink jet, the content ofthe chitosan nanofibers is preferably in a range of 0.001% to 3%, morepreferably 0.01% to 2%, and still more preferably 0.05% to 1% relativeto the total ink mass. This is because with the content of less than0.001%, the optical density and rubfastness cannot be secured, whilewith the content exceeding 3%, printability is impaired due to anincrease in ink viscosity or the like.

The chitosan nanofibers used in the present invention are notparticularly limited, and a commercial product and a product produced bya known production method can be used. Chitosan used as a raw materialof the chitosan nanofibers is manufactured and sold by many companies ofvarious countries of the world, and it is known that besides commercialproducts, chitosan with the same structure can be purified frommicroorganism bacteria or the like. The deacetylation rate of chitosanis not particularly limited and an optimum value may be properlyselected according to application. The raw material used is preferablypurified chitosan produced by deacetylating chitin possessed bycrustaceans such as crabs, shrimps, and the like and then performingprotein removal and decalcification. The chitosan nanofibers areproduced by fibrillating or refining the chitosan by grinding and/orbeating using a refiner, a high-pressure homogenizer, a medium stirringmill, a millstone, a grinder, or the like, and for example, can beproduced by a known method such as a method described in JapaneseUnexamined Patent Application Publication No. 2011-56456.

The chitosan nanofibers used in the present invention may be acommercial product. Examples of the commercial product includebio-nanofiber “BiNFi-s” chitosan of Sugino Machine Limited. Thesechitosan nanofibers can be used alone, used as a mixture of two or moretypes, or used in combination with the cellulose nanofibers.

(Aqueous Medium)

The aqueous pigment dispersion of the present invention uses an aqueousmedium such as a water-soluble solvent and/or water as a solvent. Inthis case, water may be singly used or a mixed solvent of water and awater-soluble solvent may be used. Examples of the water-soluble solventinclude ketones such as acetone, methyl ethyl ketone, methyl butylketone, methyl isobutyl ketone, and the like; alcohols such as methanol,ethanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, 2-methoxyethanol,and the like; ethers such as tetrahydrofuran, 1,4-dioxane,1,2-dimethoxyethane, and the like; amides such as dimethylformamide,N-methylpyrrolidone, and the like. A compound selected from the groupconsisting of ketones having 3 to 6 carbon atoms and alcohols having 1to 5 carbon atoms is preferably used.

Besides these, a water-soluble organic solvent capable of aqueousdissolution can also be used. Examples thereof include glycols such asethylene glycol, diethylene glycol, triethylene glycol, tetraethyleneglycol, propylene glycol, polyethylene glycol, polypropylene glycol, andthe like; diols such as butanediol, pentanediol, hexanediol, and similardiols, and the like; glycol esters such as propylene glycol laurate andthe like; ethers such as diethylene glycol monoethyl, diethylene glycolmonobutyl, diethylene glycol monohexyl, and the like; glycol ethers suchas propylene glycol ether, dipropylene glycol ether, cellosolvecontaining triethylene glycol ether, and the like; alcohols such asmethanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol,2-butanol, butyl alcohol, pentyl alcohol, similar alcohols, and thelike; sulfolane; lactones such as γ-butyrolactone and the like; lactamssuch as N-(2-hydroxyethyl)pyrrolidone and the like; other varioussolvents known as water-soluble organic solvents, such as glycerin andderivatives thereof, polyoxyethylene benzyl alcohol ether, and the like.These water-soluble organic solvents can be used alone or as a mixtureof two or more.

In particular, polyhydric alcohols such as glycols and diols with highboiling points, low volatility, and high surface tension are preferred,and glycols such as diethylene glycol, triethylene glycol, and the likeare particularly preferred.

(Anionic Group-Containing Organic Polymer Compound)

The anionic group-containing organic polymer compound used in thepresent invention is an organic polymer compound containing, forexample, a carboxyl group, a sulfonic acid group, or a phosphoric acidgroup. Examples of the anionic group-containing organic polymer compoundinclude polyvinyl resins having anionic groups, polyester resins havinganionic groups, amino resins having anionic groups, acrylic resinshaving anionic groups, epoxy resins having anionic groups, polyurethaneresins having anionic groups, polyether resins having anionic groups,polyamide resins having anionic groups, unsaturated polyester resinshaving anionic groups, phenol resins having anionic groups, siliconeresins having anionic groups, fluorine-based polymer compounds havinganionic groups, polysaccharide derivatives having anionic groups, andthe like.

In particular, acrylic resins having anionic groups and polyurethaneresins having anionic groups are preferred from the viewpoint ofabundant raw materials, ease of design, and excellent pigment dispersionfunction.

(Acrylic Resin Having Anionic Group)

Specifically, an acrylic resin having an anionic group is, for example,a resin composed of a copolymer of a monomer having an anionic group,such as (meth)acrylic acid or the like, and another ethylenicallyunsaturated monomer copolymeriable therewith. In the present invention,“(meth)acrylic acid” represents a general name of acrylic acid andmethacrylic acid. Various esters of (meth)acrylic acid are interpretedas the same as described above.

From the viewpoint that hydrophobicity of a copolymer can be enhanced atthe same acid value comparison, and adsorption of the copolymer on thepigment surfaces can be further strengthened, preferred examples of theother copolymerizable ethylenically unsaturated monomer include alkylstyrene such as styrene, α-methylstyrene, β-methylstyrene,2,4-dimethylstyrene, α-ethylstyrene, α-butylstyrene, α-hexylstyrene, andthe like; halogenated styrene such as 4-chlorostyrene, 3-chlorostyrene,3-bromostyrene, and the like; styrene-based monomers such as3-nitrostyrene, 4-methoxstyrene, vinyltoluene, and the like; and(meth)acrylic acid ester-based monomers having benzene rings, such asbenzyl (meth)acrylate, phenyl (meth)acrylate, phenylethyl(meth)acrylate, phenylpropyl (meth)acrylate, phenoxyethyl(meth)acrylate, and the like. In particular, styrene monomers such asstyrene, α-methylstyrene, tert-butylstyrene, and the like are preferablyused.

The copolymer relating to the acrylic resins having anionic groups inthe present invention may be a copolymer containing, as essentialpolymerization units, a (meth)acrylic acid polymerization unit andanother copolymerizable ethylenically unsaturated monomer polymerizationunit. The copolymer may be either a bipolymer or a terpolymer orhigher-order copolymer with a still another copolymerizableethylenically unsaturated monomer.

Examples of the ethylenically unsaturated monomer include acrylic acidesters and methacrylic acid esters such as methyl acrylate, methylmethacrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate,sec-butyl acrylate, tert-butyl acrylate, 2-ethylbutyl acrylate,1,3-dimethylbutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octylacrylate, ethyl methacrylate, n-butyl methacrylate, 2-methylbutylmethacrylate, pentyl methacrylate, heptyl methacrylate, nonylmethacrylate, and the like; acrylic acid ester derivatives andmethacrylic acid ester derivatives such as 3-ethoxypropyl acrylate,3-ethoxybutyl acrylate, dimethylaminoethyl acrylate, 2-hydroxyethylacrylate, 2-hydroxybutyl acrylate, ethyl-α-(hydroxymethyl) acrylate,dimethylaminoethyl methacrylate, hydroxyethyl methacrylate,hydroxypropyl methacrylate, and the like; acrylic acid aryl esters andacrylic acid aralkyl esters such as phenyl acrylate, benzyl acrylate,phenylethyl acrylate, phenylethyl methacrylate, and the like; polyhydricalcohol monoacrylic acid esters and monomethacrylic acid esters such asdiethylene glycol, triethylene glycol, polyethylene glycol, glycerin,bisphenol A, and the like; maleic acid dialkyl esters such as dimethylmaleate, diethyl maleate, and the like; vinyl acetate; and the like.These monomers can be added alone or two or more as a monomer component.

The copolymer relating to the acrylic resins having anionic groups inthe present invention may be a linear copolymer composed of only amonoethylenically unsaturated monomer polymerization unit or a copolymerhaving a crosslinked portion and produced by copolymerizing a smallamount of any one of various crosslinkable ethylenically unsaturatedmonomers.

Examples of the crosslinkable ethylenically unsaturated monomers includeglycidyl (meth)acrylate, divinylbenzene, and polyhydric alcoholpoly(meth)acrylates such as ethylene glycol di(meth)acrylate, propyleneglycol di(meth)acrylate, polyethylene glycol di(meth)acrylate,poly(oxyethylene-oxypropylene) glycol di(meth)acrylate, glycerinalkylene oxide-adduct tri(meth)acrylate, and the like.

In the present invention, the reaction rates or the like of the monomersused are considered to be substantially the same, and thus the feedingratios of the monomers are considered as content ratios by mass of themonomer polymerization units. The copolymer relating to the acrylicresins having anionic groups in the present invention can be synthesizedby any one of various known usual reaction methods such as bulkpolymerization, solution polymerization, suspension polymerization,emulsion polymerization, and the like. In this case, known commonpolymerization initiator, chain transfer agent (polymerization degreeadjusting agent), surfactant, and defoaming agent can be also used.

Among the copolymers described above as the copolymer relating to theacrylic resins having anionic groups used in the present invention, astyrene-acrylic acid copolymer containing a styrene monomer and(meth)acrylic acid as raw material monomers is particularly preferred,and examples thereof include a styrene-(meth)acrylic acid copolymer, astyrene-(meth)acrylic acid ester-(meth)acrylic acid copolymer, a(meth)acrylic acid ester-(meth)acyclic acid copolymer, and the like. (Inthe present invention, “styrene-acrylic acid copolymer” is defined as a“copolymer containing a styrene monomer and (meth)acrylic acid as rawmaterial monomers”. Therefore, a general-purpose monomer other than astyrene monomer and (meth)acrylic acid may be copolymerized.)

The styrene-acrylic acid copolymer is produced by copolymerizing astyrene monomer and at least one of an acrylic acid monomer and amethacrylic acid monomer, but both acrylic acid and methacrylic acid arepreferably used. The reason for this is that the uniformity of a resinis improved due to improvement in copolymerizability during resinsynthesis, resulting in good storage stability and the tendency toproduce a pigment dispersion containing finer particles.

During copolymerization, the total amount of a styrene monomer, anacrylic acid monomer, and a methacrylic acid monomer in thestyrene-acrylic acid copolymer is preferably 95% by mass or morerelative to the whole monomer components.

A usual polymerization method can be used as a method for producing thestyrene-acrylic acid copolymer, and examples thereof include methods ofperforming polymerization reaction in the presence of a polymerizationcatalyst, such as solution polymerization, suspension polymerization,bulk polymerization, and the like. Examples of the polymerizationcatalyst include 2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobisisobutyronitrile, 1,1′-azobis(cyclohexane-1-carbonitrile),benzoyl peroxide, dibutyl peroxide, butyl peroxybenzoate, and the like.The amount of use is preferably 0.1 to 10.0% by mass of the monomercomponents.

The styrene-acrylic acid copolymer may be either a random copolymer or agraft copolymer. The graft copolymer can be exemplified by a graftcopolymer in which polystyrene or a copolymer of styrene with a nonionicmonomer copolymerizable with styrene serves as a stem or a branch, and acopolymer of acrylic acid, methacrylic acid, and another monomerincluding styrene serves as a branch or stem. The styrene-acrylic acidcopolymer may be a mixture of the graft copolymer and the randomcopolymer.

In the present invention, the acrylic resins having an anionic grouppreferably have a weight-average molecular weight within a range of5,000 to 20,000. For example, when the styrene-acrylic acid copolymer isused, the weight-average molecular weight is preferably within a rangeof 5,000 to 20,000, and more preferably within a range of 5,000 to18,000. In particular, the weight-average molecular weight isparticularly preferably within a range of 5,500 to 15,000. Theweight-average molecular weight is a value measured by GPC (gelpermeation chromatography) method and is a value in terms of themolecular weight of polystyrene used as a standard material.

When the anionic group-containing organic polymer compound used in thepresent invention is the styrene-acrylic acid copolymer, the copolymerhas carboxyl groups derived from the acrylic acid monomer and themethacrylic acid monomer and preferably has an acid value of 50 to 220(mgKOH/g) and more preferably 60 to 200 (mgKOH/g). With the acid valueof 220 (mgKOH/g) or less, there is the tendency to produce lessaggregation of the pigment.

The acid value is a value measured according to Japanese IndustrialStandards “K0070:1992, Test methods for acid value, saponificationvalue, ester value, iodine value hydroxyl value, and unsaponifiablematter of chemical products” and represents an amount (mg) of potassiumhydroxide necessary for completely neutralizing 1 g of resin.

With the excessively low acid value, pigment dispersion and storagestability are decreased, and when an aqueous pigment dispersion for inkjet recording described below is prepared, printing stability isundesirably degraded. With the excessively high acid value, the waterresistance of a color recorded image is undesirably degraded. In orderto bring the acid value of the copolymer within the range,copolymerization may be performed by using (meth)acrylic acid so thatthe acid value falls within the range.

(Polyurethane Resin Having Anionic Group)

Examples of the polyurethane resins having anionic groups used in thepresent invention include polyols and polyisocyanates each having ananionic group such as a carboxyl group, a sulfonic acid group, or thelike, and urethane resins produced by further reacting general-purposepolyol not having an anionic group and a chain extender according todemand.

Example of the polyol having a carboxyl group used in the presentinvention include esters produced by reacting polyhydric alcohols withpolybasic acid anhydrides, dihydroxyalkanoic acids such as2,2-dimethylol lactic acid, 2,2-dimethylol propionic acid,2,2-dimethylol butanoic acid, 2,2-dimethylol valeric acid, and the like.Preferred compounds include 2,2-dimethlylol propionic acid and2,2-dimethylol butanoic acid. In particular, dimethylol propionic acidor dimethylol butanoic acid is preferred because of its easyavailability. Example of the polyol having a sulfonic acid group includepolyester polyols produced by reacting a dicarboxylic acid such as5-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfophthalic acid,5[4-sulfophenoxy]isophthalic acid, or the like, a salt thereof, and thelow-molecular-weight polyol described above.

Examples of the diisocyanate used in the present invention includealiphatic diisocyanate compounds such as hexamethylene diisocyanate,2,2,4-trimethylhexamethylene diisocyanate, and the like; alicyclicdiisocyanate compounds such as isophorone diisocyanate, hydrogenatedxylylene diisocyanate, 4,4-cyclohexylmethane diisocyanate, and the like;araliphatic diisocyanate compounds such as xylylene diisocyanate,tetramethylxylene diisocyanate, and the like; aromatic diisocyanatecompounds such as toluylene diisocyanate, phenylmethane diisocyanate,and the like.

Among these, aliphatic diisocyanate compounds or alicyclic diisocyanatesare preferred from the viewpoint of little photodiscoloration of aprinted image.

Examples of the general-purpose polyol not having an anionic groupinclude polyester polyol, polyether polyol, polyhydroxy polycarbonate,polyhydroxy polyacetal, polyhydroxy polyacrylate, polyhydroxypolyesteramide, polyhydroxy polythioether, and the like. Among these,polyester polyol, polyether polyol, and polyhydroxy polycarbonate arepreferred. The polyols may be reacted alone or as a mixture of two ormore.

Besides the polyol, a low-molecular-weight diol may be properly combinedfor the purpose of adjusting the film hardness or the like of a printmatter. Examples of the diol include ethylene glycol, diethylene glycol,propylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol,1,4-butanediol, and the like.

Examples of the chain extender used in the present invention includediols such as ethylene glycol, propylene glycol, 1,4-butanediol,1,6-hexanediol, 1,9-nonanediol, 1,4-bis(β-hydroxyethoxy)benzene,1,4-cyclohexanediol, xylylene glycol, and the like; diamines such asethylenediamine, propylenediamine, xylylenediamine, isophoronediamine,4,4′-diaminodiphenylmethane, tolylenediamine,4,4′-diaminodicyclohexylmethane, and the like. These can be used aloneor combination of two or more.

The polyurethane resin can be produced by producing a urethane resin byreacting the polyol and the polyisocyanate without a solvent or in thepresence of an organic solvent. Next, the urethane resin having ananionic group formed by neutralization with the basic compound or thelike is made aqueous by mixing in an aqueous medium. During the mixing,if required, the chain extender is mixed and reacted.

The reaction of the polyol with the polyisocyanate is performed, forexample, under a condition in which the equivalent ratio of isocyanategroups possessed by the polyisocyanate to hydroxyl groups possessed bythe polyol is preferably within a range of 0.8 to 2.5 and morepreferably within a range of 0.9 to 1.5.

The weight-average molecular weight of the polyurethane resin having ananionic group used in the present invention is preferably within a rangeof 5,000 to 500,000, more preferably 10,000 to 200,000, and particularlypreferably 15,000 to 100,000.

The weight-average molecular weight is a value measured by GPC (gelpermeation chromatography) method and is a value in terms of themolecular weight of polystyrene used as a standard material.

Also, the polyurethane resin used preferably has an acid value within arange of 2 to 200 (mgKOH/g) and preferably within a range of 2 to 100(mgKOH/g) for improving good water dispersion stability or the like ofthe polyurethane resin.

The acid value is a value measured according to Japanese IndustrialStandards “K0070:1992, Test methods for acid value, saponificationvalue, ester value, iodine value hydroxyl value, and unsaponifiablematter of chemical products” and represents an amount (mg) of potassiumhydroxide necessary for completely neutralizing 1 g of resin.

With the excessively low acid value, pigment dispersion and storagestability may be decreased, while with the excessively high acid value,the water resistance of a formed image may be degraded. In order tobring the acid value of the copolymer within the range, copolymerizationmay be performed by using the polyol having a carboxyl group so that theacid value falls within the range.

(Neutralizing Agent for Acryl Resin Having Anionic Group andPolyurethane Resin Having Anionic Group)

In the present invention, the acryl resin having an anionic group andthe polyurethane resin having an anionic group are preferably used afterneutralized with a basic compound. A known compound can be used as thebasic compound, and examples thereof include hydroxides of alkali metalssuch as potassium, sodium, and the like; carbonates of alkali metalssuch as potassium, sodium, and the like; carbonates of alkaline-earthmetals such as calcium, barium, and the like; inorganic basic compoundssuch as ammonium hydroxide and the like; organic basic compounds such asaminoalcohols, such as triethanolamine, N,N-dimethanolamine,N-aminoethylethanolamine, dimethylethanolamine, N—N-butyldiethanolamine,and the like; morpholines, such as morpholine, N-methylmorpholine,N-ethylmorpholine, and the like; piperazine such asN-(2-hydroxyethyl)piperazine, piperazine hexahydrate, and the like.Among these, alkali metal hydroxides represented by potassium hydroxide,sodium hydroxide, and lithium hydroxide are preferred in view ofcontribution to a decrease in viscosity of the aqueous pigmentdispersion and discharge stability of an ink for aqueous ink jetrecording, and potassium hydroxide is particularly preferred.

The neutralization rate of the anionic group with the basic compound isnot particularly limited but is generally frequently within a range of80% to 120%. In the present invention, the neutralization rate is avalue indicating an amount by % of the basic compound added relative tothe amount necessary for neutralizing all carboxyl groups in the anionicgroup-containing organic polymer compound and is calculated by a formulabelow.Neutralization rate (%)=[{mass (g) of basic compound×56.11×1000}/{resinacid value (mgKOH/g)×equivalent of basic compound×resin amount(g)}]×100  [Math. 3](Polysaccharide Derivative Having Anionic Group)

In the present invention, also, a polysaccharide derivative having ananionic group is preferably mixed with the aqueous pigment dispersion.The polysaccharide derivative having an anionic group is notparticularly limited as long as it is a polyanionic polysaccharide.Examples thereof include natural polysaccharides such as hyaluronicacid, alginic acid, pectin, polygalacturonic acid, and the like;carboxyalkyl polysaccharides such as carboxymethylpullulan,carboxymethylchitin, carboxymethylchitosan, carboxymethylmannan,carboxymethyl starch, carboxymethyl dextran, carboxyethyl cellulose,carboxymethyl pullulan, and the like; oxidized polysaccharides such asoxidized cellulose, oxidized starch, and the like; and polysaccharidescontaining sulfuric acid groups such as chondroitin sulfate, dermatansulfate, heparin and heparin sulfate, and the like. Among these,carboxymethyl cellulose and hyaluronic acid are preferred, andcarboxymethyl cellulose is particularly preferred. The weight-averagemolecular weight of the polysaccharide as a raw material is notparticularly limited but may be selected according to purpose becausethe viscosity tends to increase as the polymerization degree increases.It suffices to say that for example, the weight-average molecular weightis preferably 50,000 or more and 1,000,000 or less and more preferably50,000 or more and 500,000 or less.

In the present invention, the polysaccharide derivative having ananionic group preferably forms a salt with cation. Examples of thecation which forms a salt with the polysaccharide derivative having ananionic group include, but are not particularly limited to, proton, andmetal ions, specifically metal ions of sodium, potassium, lithium,calcium, magnesium, and the like; and organic cations such as organicammonium and the like. Among these, carboxymethyl cellulose sodium saltand carboxymethyl cellulose ammonium salt are preferred because they canbe easily obtained and the intended purpose can be easily obtained, andthe carboxymethyl cellulose ammonium salt is particularly preferredbecause of the large viscosity decreasing effect. Of course, thesepolysaccharide derivatives having anionic groups can be used alone or incombination of two or more.

The degree of etherification (also referred to as a “degree ofsubstitution” DS) and the degree of neutralization of the polysaccharidederivative having an anionic group, particularly carboxymethyl cellulosesodium salt or ammonium salt, used in the present invention are notparticularly limited but are preferably adjusted so that the viscosityof a 1 mass % aqueous solution measured by a B-type viscometer at arotor rotational speed of 60 rpm and 25° C. is 300 to 7000 mPa·s andmore preferably 500 to 5000 mPa·s. With the viscosity exceeding 7000mPa·s, uniform pigment dispersion tends to become difficult, and theviscosity of the resultant ink is excessively increased, thereby causingpractical disadvantage. On the other hand, with the viscosity of lessthan 300 mPa·s, significant improvement in adhesion and rubfastness to amedium tends to be hardly recognized, thereby causing disadvantage.

The “degree of etherification” is a value indicating an average numberof hydroxyl groups, to which carboxymethyl groups are ether-bonded,among the three hydroxyl groups contained in anhydrous glucose servingas a cellulose constitution unit in carboxymethyl cellulose. Therefore,the value is theoretically between 0 and 3.

The degree of etherification of carboxymethyl cellulose sodium salt orammonium salt used in the present invention is preferably 0.5 to 2, morepreferably 0.6 to 1.6, and still more preferably 0.8 to 1.4. This isbecause the degree of etherification of 0.8 or more causes saltresistance. The upper limit of the degree of etherification istheoretically 3, and the degree of etherification exceeding 2 causesdifficulty in stable production, while the degree of etherification ofless than 0.4 causes difficulty in dissolving in an aqueous medium andthus causes low practicality.

The degree of etherification can be determined, for example, accordingto a CMC Industry Association analytical method (ashing method). First,1 g of carboxymethyl cellulose is weighed, placed in a magneticcrucible, and ashed at 600° C., and the sodium oxide produced by ashingis titrated with 0.05 mol/L sulfuric acid using phenolphthalein as anindicator. The degree of etherification can be determined by calculationaccording to a formula below in which a titer A (mL) per g ofcarboxymethyl cellulose is introduced.Degree of etherification=(162×A)/(10,000−80×A)  [Math. 4]

For a commercial product, a value described in a catalogue can bedirectly used.

The amount of the polysaccharide derivative having an anionic groupmixed is not particularly limited and appropriately determined accordingto the purpose described above. For example, for the purpose ofimproving the color development (optical density) of the formed imageand the rubfastness of the image, the amount of the polysaccharidederivative having an anionic group is preferably 5 parts by mass orless, more preferably 3 parts by mass or less, and most preferably 2parts by mass or less relative to 1 part by mass of cellulose crystal.

The carboxymethyl cellulose sodium or carboxylmethyl cellulose ammoniumused may be a commercial product. Examples thereof include Serogenseries sold by DKS Co., Ltd., CMC Daicel series sold by Daicel FineChemLtd., Sunrose F series sold by Nippon Paper Chemicals Co., Ltd., and thelike. Also, DN series sold by Daicel FineChem Ltd. can be used as thecarboxymethyl cellulose ammonium.

In the case of the aqueous pigment dispersion, particularly for ink jet,the content (mass basis) of the anionic group-containing organic polymercompound used in the present invention is preferably within a range of0.1% to 10%, more preferably 0.3% to 5%, and still more preferably 0.5%to 2% relative to the total mass of ink. This is because with thecontent of less than 0.1%, rubfastness cannot be secured, while with thecontent exceeding 10%, printability is degraded due to an increase inviscosity or the like.

The anionic group-containing organic polymer compound is mainly used forthe purpose of dispersing the pigment, but the compound has the functionas a binder because it is a polymer.

Of course, a commercial product can also be used. Examples of thecommercial product include Ajisper PB series of Ajinomoto Fine-TechnoCo., Inc., DISPERBYK series and BYK series of BYK Co., Ltd., Efka seriesof BASF Corporation, and the like.

(Method for Producing Aqueous Pigment Dispersion)

A method for producing the aqueous pigment dispersion of the presentinvention is not particularly limited, and a known method can be used.That is, bio-nanofibers or the like can be mixed with desired timingregardless of before or after medialess dispersion described below.Examples of the method include (1) a method for preparing an aqueouspigment dispersion containing at least the pigment, the bio-nanofibers,etc. of the present invention and, if required, other additives addedthereto, by medialess dispersion,

(2) a method for preparing an aqueous pigment dispersion by forming ahigh-concentration pigment aqueous dispersion (pigment paste) inadvance, and then diluting the prepared aqueous dispersion with anaqueous medium and, at the same time, adding the bio-nanofibers and, ifrequired, other additives, and the like.

(1) Medialess Dispersion of Aqueous Pigment Dispersion

In the present invention, examples of the medialess dispersion includean ultrasonic dispersion method, and dispersion methods using ahigh-speed disc impeller, a colloid mill, a roll mill, a high-pressurehomogenizer, a nanomizer, an altimizer, or the like. In view ofproductivity and contamination (mixing and contamination with foreignmatter) due to wearing of a medium, the ultrasonic dispersion method ispreferred. In the present invention, an example using the ultrasonicdispersion method is described in detail below.

It is preferred to mix and stirrer the pigment and the aqueous mediumbefore ultrasonic dispersion in order to enhance flowability or preventsettling of the pigment, but this is not essential and a mixing-stirringapparatus is not particularly limited.

Also, from the viewpoint of securing flowability, the viscosity ispreferably within a range of 0.1 to 100 mPa·s, more preferably 0.5 to 50mPa·s, still more preferably 0.5 to 30 mPa·s, and most preferably 1.0 to20 mPa·s. In this case, the pigment concentration is preferably 1% to30% by mass, more preferably 1% to 25% by mass, still more preferably 3%to 20% by mass, and most preferably 5% to 20% by mass.

Ultrasonic irradiation conditions are not particularly limited, but theirradiation can be preferably performed at an output of 100 to 3000 Wand a frequency of 15 to 40 kHz and more preferably at an output of 150to 2000 W and a frequency of 15 to 30 kHz.

At the output and frequency within the respective ranges describedabove, a dispersion step by cavitation can be effectively performed, andthe number of coarse particles in the aqueous pigment dispersion isdecreased, thereby improving chroma (texture) of a color film obtainedfrom the aqueous pigment dispersion and permitting smooth discharge(good discharge stability) in ink jet printing with aqueous ink usingthe aqueous pigment dispersion. Further, the output and frequency arevery preferred for the reasons that the quality of a product is notdecreased by settling of the pigment particles or the like, that erosionof an oscillating rod is significantly decreased to decrease themaintenance cost of the device used, and the like.

A time necessary and sufficient for actually uniformly dispersingpigment particles, bio-nanofibers, etc. in the aqueous pigmentdispersion may be secured as the time of ultrasonic irradiation. Anamount of electric power of 5 to 100 W/g is generally applied to themass of the pigment contained in the dispersion. Of course, ultrasonictreatment may be performed for a longer time or stopped in a short time.The ultrasonic treatment time is preferably selected within a range inwhich no trouble occurs in performance such as the dispersed particlediameter, viscosity, image clearness, and the like according to the typeof the pigment, and consideration is made to prevent a decrease inproductivity with time.

After the ultrasonic irradiation, if required, the aqueous pigmentdispersion can be further dispersed. Also, dispersion and ultrasonicirradiation can be repeatedly performed.

Any one of various known system devices can be used as a dispersingdevice which can be used in the dispersion step, and the dispersingdevice is not particularly limited. Examples of the device include mediadispersion devices such as a sand mill, a beads mill, a pebble mill, aball mill, a pearl mill, a basket mill, an attritor, a Dyno-mill, a boremill, a visco-mill, a motor mill, a SC mill, a dry mill, a paintconditioner, and the like; and medialess dispersing devices such as ahigh-speed disc impeller, a colloid mill, a high-pressure homogenizer, ananomizer, an altimizer, and the like. However, it should be noted thatas described above, unnecessary physical damage may be caused on thepigment surfaces.

The temperature of the aqueous pigment dispersion subjected toultrasonic irradiation is not particularly limited but the ultrasonicirradiation is preferably performed while the aqueous pigment dispersionis controlled to the freezing point to 70° C. This is because at atemperature equal to or lower than the freezing point, ultrasonicdispersion becomes impossible, while at a temperature 70° C. or higher,an uncertain condition such as an increase in pigment concentrationoccurs due to water evaporation or the like.

A known method of ice cooling, air cooling, water cooling, or the likecan be generally used as a method for cooling the aqueous pigmentdispersion during ultrasonic irradiation. Examples of the method includea method of flowing a refrigerant in a jacket of a vessel in which theaqueous pigment dispersion is placed, a method of immersing a vesselcontaining the aqueous pigment dispersion in a refrigerant, a method ofspraying gas wind, a method of cooling by evaporation heat using arefrigerant, such as water, and wind, and the like.

For example, a method using, as a refrigerant, cooling water previouslycooled to over 0° C. and 20° C. or lower and preferably over 0° C. and10° C. or lower is a desired method because it is relatively economicaland has an excellent cooling efficiency. In this case, the cooling watercan be circulated by a circulating device, and at the same time, coolingcan be performed with a cooling device. In this case, it is verypreferred to cause freezing-point depression by adding, to the coolingwater, ethylene glycol, diethylene glycol, or the like which decreasesthe freezing temperature, or adding sodium chloride or the like. As aresult, even when a satisfactory cooling effect cannot be obtained bycooling water of over 0° C., the cooling water at a temperature lowerthan this can be produced, and thus ultrasonic irradiation can beperformed while the aqueous pigment dispersion is maintained at a lowertemperature with the temperature range described above. Even in the caseof air cooling, instead of simply spraying wind at an ambienttemperature, cold air previously cooled is preferably used.

In relation to cost, the ultrasonic irradiation is preferably performedby using as few devices as possible but, if required, a minimum numberof devices can be connected in series or parallel for treatment.

The end point of ultrasonic irradiation may be determined by measuringthe particle diameters of the pigment particles and the compositeparticles using a particle gauge or a commercial particle diametermeasuring device, or by measuring physical properties such as viscosity,contact angle, reflected luminous intensity and hue of coating filmsprepared by various methods, etc. Also, the end point may be determinedby direct observation with a microscope or the like.

(2) Method Passing Through High-Concentration Aqueous Pigment Dispersion(Pigment Paste)

A method for previously forming the pigment paste is not particularlylimited, and a known dispersion method can be used.

Examples of the method for preparing the pigment paste include methods(i) to (iii) below.

(i) A method of adding a pigment to an aqueous medium containing apigment dispersant and water and then dispersing the pigment in theaqueous medium by using a stirring/dispersion device to prepare apigment paste.

(ii) A method of kneading a pigment and a pigment dispersant by using akneader such as a two-roll, a mixer, or the like, and then adding theresultant kneaded product to an aqueous medium containing water toprepare a pigment paste by using a stirring/dispersion device.

(iii) A method of adding a pigment to a solution prepared by dissolvinga pigment dispersant in an organic solvent having compatibility withwater, such as methyl ethyl ketone, tetrahydrofuran, or the like,dispersing the pigment in the organic solution by using astirring/dispersion device, next performing phase-inversionemulsification using an aqueous medium, and then distilling off theorganic solvent to prepare a pigment paste.

Examples of the kneader include, but are not particularly limited to, aHenschel Mixer, a pressure kneader, a Banbury mixer, a planetary mixer,and the like.

Examples of the stirring/dispersion device include, but are notparticularly limited to, an ultrasonic homogenizer, a high-pressurehomogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, asand grinder, a Dyno-mill, Dispermat, a SC mill, a nanomizer, and thelike. These devices may be used alone or in combination of two or more.

The amount of the pigment contained in the pigment paste is preferably5% to 60% by mass and more preferably 10% to 50% by mass. When theamount of the pigment is less than 5% by mass, there is a tendency thatcoloring of the aqueous pigment dispersion and aqueous ink prepared byusing the pigment paste is unsatisfactory, and a satisfactory imagedensity cannot be obtained. Conversely, when the amount exceeds 60% bymass, the dispersion stability of the pigment in the pigment paste tendsto be decreased.

Also, remaining coarse particles cause deterioration in various imagecharacteristic, and thus the coarse particles are preferably properlyremoved by centrifugal separation or filtration treatment or the likeafter preparation of an ink.

After the dispersion step, post-treatment may be performed through astep of removing impurities by ion exchange treatment orultra-treatment. Ionic substances (divalent metal ions and the like)such as cation and anion can be removed by ion exchange treatment, andimpurity dissolved materials (residual materials of pigment synthesis,excessive components in the dispersion composition, resins not adsorbedon the organic pigment, mixed foreign matters, etc.) can be removed byultra-treatment. The ion exchange treatment uses a known ion-exchangeresin. The ultra-treatment uses a known ultrafiltration membrane whichmay be a usual type or two-times capacity-up type.

(Aqueous Ink for Ink Jet Recording)

If required, the aqueous pigment dispersion can be diluted with awater-soluble solvent with any desired timing, or a wetting agent(drying inhibitor), a penetrant, or another additive, that is, a knowncommon additive, can be added. The addition permits use for variousapplications such as the automobile or construction coating field, theprinting ink field of offset inks, gravure inks, flexo inks, silk screeninks, and the like, the field of inks for ink jet printing, and thelike. After preparation of an ink, a centrifugal separation orultrafiltration treatment step can be added for removing coarseparticles. Herein, an aqueous ink for ink jet recording is described indetail.

(Wetting Agent)

The wetting agent is added for the purpose of preventing drying of theink. The content of the wetting agent for the purpose of preventingdrying in the ink is preferably 3% to 50% by mass.

The wetting agent used in the present invention is not particularlylimited and preferably has miscibility with water and the effect ofpreventing clogging of a head of an ink jet printer. Examples thereofinclude glycerin, ethylene glycol, diethylene glycol, triethyleneglycol, polyethylene glycol having a molecular weight of 2000 or less,propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propyleneglycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol,1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, mesoerythritol,pentaerythritol, and the like. In particular, when propylene glycol or1,3-butyl glycol is contained, safety and the excellent effect on iondrying properties and discharge performance can be achieved.

(Penetrant)

The penetrant is added for the purpose of improving the penetration intoa recording medium and adjusting the dot diameter on a recording medium.

Examples of the penetrant include lower alcohols such as ethanol,isopropyl alcohol, and the like, alkyl alcohol ethylene oxide adductssuch as ethylene glycol hexyl ether, diethylene glycol butyl ether, andthe like, alkyl alcohol propylene oxide adducts such as propylene glycolpropyl ether and the like.

The content of the penetrant in the ink is preferably 0.01% to 10% bymass.

(Surfactant)

The surfactant is added for adjusting ink characteristics such assurface tension and the like. Examples of the surfactant which can beadded include, but are not particularly limited to, various anionicsurfactants, nonionic surfactants, cationic surfactants, and amphotericsurfactants, and the like. Among these, the anionic surfactants and thenonionic surfactants are preferred.

Examples of the anionic surfactants include alkylbenzenesulfonic acidsalts, alkylphenylsulfonic acid salts, alkylnaphthalenesulfonic acidsalts, higher fatty acid salts, sulfuric acid ester salts of higherfatty acid esters, sulfonic acid salts of higher fatty acid esters,sulfuric acid ester salts and sulfonic acid salts of higher alcoholethers, higher alkyl sulfosuccinic acid salts, polyoxyethylene alkylether carboxylic acid salts, polyoxyethylene alkyl ether sulfuric acidsalts, alkylphosphoric acid salts, polyoxyethylene alkyl etherphosphoric acid salts, and the like. Specific examples thereof includedodecylbenzenesulfonic acid salts, isopropylnaphthalenesulfonic acidsalts, monobutylphenylphenol monosulfonic acid salts,monobutylbiphenylsulfonic acid salts, dibutylphenylphenol disulfonicacid salts, and the like.

Examples of the nonionic surfactants include polyoxyethylene alkylethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acidesters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acidesters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acidesters, polyoxyethylene glycerin fatty acid esters, polyglycerin fattyacid esters, sucrose fatty acid esters, polyoxyethylene alkylamines,polyoxyethylene fatty acid amides, fatty acid alkylolamides,alkylalkanol amides, acetylene glycol, acetylene glycol oxyethyleneadduct, polyethylene glycol-polypropylene glycol block copolymers, andthe like. Among these, preferred are polyoxyethylene nonyl phenyl ether,polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenylether, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters,sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters,fatty acid alkylolamides, acetylene glycol, acetylene glycol oxyethyleneadduct, and polyethylene glycol-propylene glycol block copolymers.

Other examples of the surfactant which can be used includesilicone-based surfactants such as polysiloxane oxyethylene adduct;fluorine-based surfactants such as perfluoroalkylcarboxylic acid salts,perfluoroalkylsulfonic acid salts, and oxyethylene perfluoroalkylethers; bio-surfactants such as spiculisporic acid, rhamnolipid, andlysolecithin, and the like.

These surfactants can be used alone or as a mixture of two or more. Whenthe surfactant is added, the adding amount is preferably within a rangeof 0.001% to 2% by mass, more preferably within a range of 0.001% to1.5% by mass, and still more preferably within a range of 0.01% to 1% bymass relative to the total mass of ink. When the amount of thesurfactant added is less than 0.001% by mass, there is a tendency thatthe effect of addition of the surfactant cannot be obtained, while whenthe amount of use exceeds 2% by mass, the problem of image blurring orthe like easily occurs.

If required, an antiseptic agent, a viscosity adjuster, a pH adjuster, achelating agent, a plasticizer, an antioxidant, an ultraviolet absorber,and the like can also be added.

(Recording Media)

The aqueous pigment dispersion of the present invention exhibits a highoptical density and rubfastness, particularly, for plain paper. Ofcourse, the aqueous pigment dispersion may be used for other absorbentrecording media. Examples of a water absorbent recording medium includeplain paper, (fine) coated paper, cloth, paper for exclusive use for inkjet, ink jet glossy paper, corrugated cardboard, wood, and the like.

EXAMPLES

The present invention is described in detail by giving examples below.

In addition, “parts” and “%” are “parts by mass” and “% by mass”,respectively, unless otherwise specified.

<Bio-Nanofibers>

The bio-nanofibers shown in Table 1 were used.

TABLE 1 Bio-nanofiber Cellulose nanofiber Cellulose nanofiber Chitosannanofiber Product name Celish BiNFi-s BiNFi-s KY100G 2% cellulosechitosan Maker Daicel FineChem Sugino Machine Sugino Machine Ltd.Limited Limited Product name CEL-KY CEL-NF CHI-NF (abbreviation) Aspectratio 160 270 430 Mode diameter 340 nm 410 nm 320 nm 80% particlediameter/  5.7  5.3  5.3 20% particle diameter Specific surface area —2059 cm²/cm³ 1959 cm²/cm³ Degree of 58% — — crystallization Amount ofcarboxyl Less than 0.1 mmol/g Less than 0.1 mmol/g — group

The average fiber diameter and aspect ratio are calculated from theresults of SEM analysis. Specifically, a bio-nanofiber dispersion wascast on a wafer and observed with SEM, and fiber diameter and fiberlength values of 20 or more fibers per image are read. This wasperformed for images of at least three regions which were not overlappedwith each other, to obtain information of the fiber diameters and fiberlengths of at least 30 fibers. The average fiber diameter was calculatedto two significant figures from the date of fiber diameters. The averagefiber length was calculated from the date of fiber lengths, and theaspect ratio was calculated to two significant figures by aspectratio=average fiber diameter/average fiber length.

The mode diameter and (80% particle diameter/20% particle diameter) werecalculated to two significant figures from measurement values (volumebasis) of 0.1% by mass of bio-nanofibers (solvent:water, temperature 25°C.) by using dynamic light scattering Nanotrac particle size analyzerUPA-150EX (manufactured by Nikkiso Co., Ltd.).

The specific surface area was calculated from particle size distributionvalues measured by a light scattering method using laserdiffraction/scattering particle size distribution analyzer LA-960(manufactured by Horiba, Ltd.). The measurement conditions are givenbelow.

Measurement range: 0.01 μm to 3,000 μm, measurement method: wet method,basis of the particle diameter: volume, dispersion medium: pure water

Sample refractive index: 1.56 to 0.00i, dispersion medium refractiveindex: 1.333 to 0.00i

Dispersion treatment: built-in ultrasonic waves (30 W) 1 minute,circulation speed: 3, stirring speed: No

Transmittance (semiconductor laser beam) and transmittance (LED light):80% or more

The degree of crystallization of cellulose was calculated according to aformula below from the diffraction intensity of a 002 plane at 2θ=22.6°and the diffraction intensity of an amorphous portion at 2θ=18.5° usingthe diffraction intensity at 2θ=4° to 32° as a baseline in a diffractionchart obtained by measurement of X-ray crystal diffraction (apparatus:RINT-2000 (manufactured by Rigaku Corporation)) at a measurement voltageof 40 kV, a measurement current of 50 mA, and a scan speed of 2°/min.χ_(c)=(I _(002c) −I _(a))/I _(002c)×100  [Math. 5]

(In the formula, χ_(c) represents the degree of crystallization of typeI cellulose (%), I_(002c) represents the 002 plane diffraction intensityat 2θ=22.6°, and I_(a) represents the amorphous portion diffractionintensity at 2θ=18.5°.)

<Anionic Group-Containing Organic Polymer Compound>

The following compounds were used as the anionic group-containingorganic polymer compound.

(Polysaccharide Derivative Having Anionic Group)

Commercial products were used.

CMC139O (manufactured by Daicel FineChem Ltd.): sodium carboxylmethylcellulose (etherification degree, 1.0 to 1.5)

DN-800H (manufactured by Daicel FineChem Ltd.): ammonium carboxylmethylcellulose

DN-100L (manufactured by Daicel FineChem Ltd.): ammonium carboxylmethylcellulose

DN-10L (manufactured by Daicel FineChem Ltd.): ammonium carboxylmethylcellulose

(Acrylic Resin Having Anionic Group)

Production Example 101: Solution (SA-1) of Acrylic Resin Having AnionicGroup

A resin A having a monomer composition ratio (styrene/methacrylicacid/acrylic acid) of 77/13/10 (mass ratio), a weight-average molecularweight of 8800, an acid value of 150 mgKOH/g, and a glass transitiontemperature of 107° C. was produced. Then, 87.4 parts of ion exchangewater and 22 g of a 34 mass % aqueous potassium hydroxide (KOH) solutionwere added to 50 parts of methyl ethyl ketone (abbreviated as “MEK”hereinafter) and 50 parts of the resin A, and the resultant mixture wassufficiently stirred to prepare a resin solution. Then, MEK was removedfrom the resin solution at a water bath temperature of 45° C. under areduced pressure condition of 40 hPa, thereby preparing a solution(SA-1) of an acrylic resin having an anionic group with a resin soldcontent of 20%.

(Polyurethane Resin Having Anionic Group)

Production Example 102: Solution (UR-1) of Polyurethane Resin HavingAnionic Group

In a vessel replaced with nitrogen and provided with a thermometer, anitrogen gas inlet tube, and a stirrer, 64.2 parts by mass of methylethyl ketone was added, and 18.4 parts by mass of 2,2-dimethylolpropionic acid and 33.9 parts by mass of isophorone diisocyanate weremixed in the methyl ethyl ketone, followed by reaction at 80° C. for 4hours. Four hours after, 38.2 parts by mass of methyl ethyl ketone wasfurther supplied and the resultant mixture was cooled to 60° C. orlower, and 140.1 parts by mass of polyether polyol (“PTMG2000”polytetramethylene glycol manufactured by Mitsubishi ChemicalCorporation, number-average molecular weight 1,000) and 0.01 parts bymass of dibutyltin dilaurate (hereinafter “DBTDL”) were added andcontinuously reacted at 80° C.

After it was confirmed that the weight-average molecular weight of thereaction product reached a range of 20,000 to 50,000, the reaction isterminated by adding 1.3 parts by mass of methanol. Next, 41.6 parts bymass of methyl ethyl ketone was added to the reaction product to preparean organic solvent solution of urethane resin.

The carboxyl groups possessed by the urethane resin were partially orentirely neutralized by adding 15.1 parts by mass of a 50 mass % aqueouspotassium hydroxide solution to the urethane resin organic solventsolution. Next, 848.5 parts by mass of water was added and sufficientlystirred to produce a mixture containing the urethane resin, methyl ethylketone, and water, the urethane resin being dispersed or dissolved inthe water.

Next, after aging of the mixture for about 2 hours, 0.07 parts by massof Surfynol 440 (manufactured by Air Products and Chemicals, Inc.,acetylene glycol ethylene oxide adduct, nonvolatile content 100% bymass) was added to the mixture and stirred for about 20 minutes toproduce a mixture, which was then distilled under a reduced pressurecondition of about 1 to 50 kPa.

After it was confirmed that 144 parts by mass of methyl ethyl ketonecontained in the mixture was removed, 0.03 parts by mass of Surfynol 440(manufactured by Air Products and Chemicals, Inc.) was added underreduced pressure, and then distillation under reduced pressure wascontinued. Next, after it was confirmed that 147 parts by mass of watercontained in the mixture was removed, the reduced-pressure distillationwas terminated.

Next, the nonvolatile content was adjusted by adding water to prepare asolution (UR-1) of a polyurethane resin having an anionic group with aresin sold content of 20% by mass.

<Pigment or the Like>

Commercial products below were used as the pigment or the like.

(Pigment)

#960 (manufactured by Mitsubishi Chemical Corporation): carbon black

FASTOGEN Blue TGR (manufactured by DIC Corporation): C.

I. Pigment Blue 15:3

FASTOGEN Super Magenta RY (manufactured by DIC Corporation): C. I.Pigment Red 122

Fast Yellow 7413 (manufactured by Sanyo Color Works, Ltd.): C. I.Pigment Yellow 74

(Self-Dispersion Type Pigment Dispersion)

Pigment dispersions below were used as a self-dispersion type pigmentdispersion.

CAB-O-JET 400 Black Colorant (United States Cabot Corporation)

CAB-O-JET 450C Cyan Colorant (United States Cabot Corporation)

CAB-O-JET 465M Magenta Colorant (United States Cabot Corporation)

CAB-O-JET 470Y Yellow Colorant (United States Cabot Corporation)

SENSIJET BLACK SDP100 (manufactured by United States Sensient ColorsInc.)

Production Example 1: Method for Producing Ultrasonic Dispersion (US)Aqueous Black Pigment Dispersion

In a metal beaker, 20 parts of “#960” (carbon black manufactured byMitsubishi Chemical Corporation), 20 parts of the solution (SA-1) of theanionic group-containing organic polymer compound, 5 parts oftriethylene glycol, and water were added so that a total amount was 100parts, and the resultant mixture was manually stirred. Then, ultrasonicdispersion was performed with an ultrasonic disperser (UP200Stmanufactured by Hielscher Company, operation frequency: 26 KHz,operation output: 160 W) for 10 minutes. After the ultrasonic dispersiontreatment, 1.0 part (in terms of solid content) of bio-nanofibers“BiNFi-s 2% cellulose” (manufactured by Sugino Machine Limited, productname (abbreviation): CEL-NF), and pure water were added to 100 parts ofthe mixture so that a total amount was 250 parts, followed by manualstirring. Then, ultrasonic dispersion treatment was performed with anultrasonic disperser (UP200St manufactured by Hielscher Company,operation frequency: 26 KHz, operation output: 160 W) for 25 minutes toproduce an aqueous black pigment dispersion (corresponding to a pigmentconcentration of 8%).

Production Examples 2 to 4: Method for Producing Ultrasonic Dispersion(US) Aqueous Cyan Pigment Dispersion

An aqueous cyan pigment dispersion was prepared by the same method asdescribed above except that the type of the pigment used, the type ofthe anionic group-containing organic polymer compound used, and the typeand amount of the bio-nanofibers used were changed to those described ineach of examples.

Table 2 shows examples of the amount of ultrasonic dispersion (US)aqueous pigment dispersion added. When a self-dispersion type pigmentwas used as the pigment, bio-nanofibers or the like were added to adispersion of the self-dispersion type pigment so as to prepare apredetermined composition.

TABLE 2 Production of ultrasonic dispersion (US) aqueous pigmentdispersion Production Production Production Production Example 1 Example2 Example 3 Example 4 (Black) (Cyan) (Magenta) (Yellow) Pigment Productname #960 FASTOGEN FASTOGEN Fast Yellow Blue TGR Super Magenta 7413 RY(parts) 20 20 20 20 Solution of anionic group-containing 20 30 30 20Organic polymer compound (SA-1) (parts) Triethylene glycol (parts) 5 2020 20 Pure water Balance Balance Balance Balance Sub-total (parts) 100100 100 100 Bio-nanofiber Product name CEL-NF CHI-NF CHI-NF CEL-NF(abbreviation) (parts) 1.0 0.25 0.25 1.0 Pure water Balance BalanceBalance Balance Total (parts) 250 250 250 250

Preparation Example 1: Ultrasonic Dispersion (US) Aqueous Black Ink(Type 1)

First, 25 parts of pure water was added to 75 parts of the aqueouspigment dispersion (corresponding to a pigment concentration of 8%)produced in Production Example 1 and stirred by using a magneticstirrer, and then the resultant mixture was filtered with a 1.2 μmmembrane filter to produce an ultrasonic dispersion (US) aqueous blackink (Type 1) of Example 1. The physical properties and the like of theprepared ink are described in tables below.

Preparation Example 2: Ultrasonic Dispersion (US) Aqueous Black Ink(Type 2)

First, 50 parts of separately prepared vehicle (mixing ratio by mass:2-pyrrolidone/triethylene glycol monobutyl ether/glycerin/Surfynol440/pure water=16/16/6/1/61) was added to 50 parts of the aqueouspigment dispersion (corresponding to a pigment concentration of 8%)produced in Production Example 1 and stirred by using a magneticstirrer, and then the resultant mixture was filtered with a 1.2 μmmembrane filter to produce an ultrasonic dispersion (US) aqueous blackink (Type 2) of Example 14. The physical properties and the like of theprepared ink are described in tables below.

An ultrasonic dispersion (US) aqueous cyan ink (Type 1) was preparedaccording to Preparation Example 1 or the like described above exceptthat the type of the pigment used, the type of the anionicgroup-containing organic polymer compound used, and the type and amountof the bio-nanofibers used were changed to those described in each ofexamples. The physical properties and the like of the prepared ink aredescribed in tables below.

Production Example 5: Method for Producing Kneading Method (PLM) AqueousBlack Pigment Dispersion

In a planetary mixer (ACM04LVTJ-B, manufactured by AicohshaManufacturing Co., Ltd.), a mixture (50 parts of carbon black “#960”(manufactured by Mitsubishi Chemical Corporation), 10 parts of anionicgroup-containing organic polymer compound (resin A), 4.4 parts of a 34%aqueous potassium hydroxide solution, and 50 parts of triethyleneglycol) was added, and the mixture was kneaded for 60 minutes at ajacket temperature of 60° C. and a stirring blade rotational speed of 25rpm (number of revolutions: 80 rpm). Further, the whole of the resultantkneaded product was placed in a domestic mixer (Healthy Mix manufacturedby Zojirushi Corporation), and 218.6 parts of pure water was added.After the mixer was hermetically sealed, the resultant mixture wasstirred and dissolved for 20 minutes to produce 333 parts of an aqueousmixture MX. In a metal beaker, 53.33 parts of the aqueous mixture MX,0.3 parts (in terms of solid content) of bio-nanofibers “BiNFi-sChitosan” (manufactured by Sugino Machine Limited, product name(abbreviation): CHI-NF), and pure water were added so that a totalamount was 100 parts, stirred and mixed by a homogenizer (Rotor/Statormanufactured by Silverson Machines Ltd.) at 8000 rpm for 11 minutes, andfurther diluted with pure water to prepare a kneading method (PLM)aqueous black pigment dispersion (corresponding to a pigmentconcentration of 8%).

Production Examples 6 to 8: Method for Producing Kneading Method (PLM)Aqueous Cyan Pigment Dispersion

A kneading method (PLM) aqueous cyan pigment dispersion was preparedaccording to the production method described above except that the typeof the pigment used, the type of the anionic group-containing organicpolymer compound used, and the type and amount of the bio-nanofibersused were changed to those described in each of examples. Table 3 showsexamples of the amount of kneading method (PLM) aqueous pigmentdispersion added.

TABLE 3 Production of kneading method (PLM) aqueous pigment dispersionProduction Production Production Production Example 5 Example 6 Example7 Example 8 (Black) (Cyan) (Magenta) (Yellow) Pigment Product name #960FASTOGEN FASTOGEN Fast Yellow Blue TGR Super 7413 Magenta RY (parts) 5050 50 50 Anionic group-containing organic 10 15 10 15 polymer compoundResin A (parts) Triethylene glycol (parts) 50 18.75 33.5 27.5 34%aqueous potassium hydroxide 4.4 6.6 4.4 6.6 solution Pure water BalanceBalance Balance Balance Aqueous mixture MX (parts) 333 333 333 333 ↓ ↓ ↓↓ Aqueous mixture MX (parts) 53.33 53.33 53.33 53.33 Bio-nanofiberProduct name CHI-NF CHI-NF CEL-KY CHI-NF (abbreviation) (parts) 0.3 0.30.2 0.1 Anionic group- Product name — DN-800H — — containing organic(parts) — 0.4 — — polymer compound Pure water Balance Balance BalanceBalance Total (parts) 100 100 100 100

Preparation Example 3: Kneading Method (PLM) Aqueous Black Ink (Type 1)

First, 12.5 parts of pure water was added to 37.5 parts of the aqueouspigment dispersion (corresponding to a pigment concentration of 8%)produced in Production Example 5 and stirred by using a magneticstirrer, and then the resultant mixture was filtered with a 1.2 μmmembrane filter to produce a kneading method (PLM) aqueous black ink(Type 1) of Example 11. The physical properties and the like of theprepared ink are described in tables below.

Preparation Example 4: Kneading Method (PLM) Aqueous Black Ink (Type 2)

First, 25 parts of separately prepared vehicle (mixing ratio by mass:2-pyrrolidone/triethylene glycol monobutyl ether/glycerin/Surfynol440/pure water=16/16/6/1/61) was added to 25 parts of the aqueouspigment dispersion (corresponding to a pigment concentration of 8%)produced in Production Example 5 and stirred by using a magneticstirrer, and then the resultant mixture was filtered with a 1.2 μmmembrane filter to produce a kneading method (PLM) aqueous black ink(Type 2) of Example 47. The physical properties and the like of theprepared ink are described in tables below.

A kneading method (PLM) aqueous cyan ink (Type 1) or the like wasprepared according to Preparation Example 3 or the like described aboveexcept that the type of the pigment used, the type of the anionicgroup-containing organic polymer compound used, and the type and amountof the bio-nanofibers used were changed to those described in each ofexamples. The physical properties and the like of the prepared ink aredescribed in tables below.

<Measurement of Ink Physical Properties>

(pH Measurement Method)

Measurement (ink temperature of 25° C.) was performed by using MM-60R(manufactured by DKK-TOA Corporation).

(Viscosity Measurement Method)

Measurement (ink temperature of 25° C.) was performed by usingViscometer TV-20 (manufactured by Toki Sangyo Co., Ltd.).

(Measurement Method for Average Particle Diameter)

Measurement (ink temperature of 25° C.) was performed by using a dynamiclight scattering Nanotrac particle size analyzer UPA-150EX (manufacturedby Nikkiso Co., Ltd.). A volume-based (Mv) median diameter (D₅₀) wasused as an average particle diameter.

<Evaluation of Printed Matter>

(Measurement of Optical Density (O. D.) Value)

The prepared ink was applied to PPC paper by using wire bar #3. Afternatural drying for 24 hours, the optical density (O. D.) of a coatedproduct was measured. Measurement was performed by using “Gretag MacbethSpectro Scan Transmission” (United States X-Rite Inc.), and an averagevalue obtained by measurement of a total 9 points of a 3 by 3 matrix wasused as the optical density (O. D.) value of the coated product.

In addition, with respect to improvement in the optical density, theoptical density (O. D.) was calculated by a formula below and evaluatedbased on evaluation criteria below.(Optical density (O.D.) of sample ink)/(Optical density (O.D.) ofreference ink)×100(%)  [Math. 6](Determination Criteria)

G: Improvement of 3% or more in optical density

N: No improvement of 3% or more in optical density

(Rubfastness Test)

The prepared ink was applied to glossy paper by using wire bar #3. Afternatural drying for 24 hours, the coated surface was rubbed with a 45Rfriction block on which PPC paper for friction was wound using aGakushin-type rubbing tester (manufactured by Daiei Kagaku Seiki Mfg.Co., Ltd.) under the conditions including a load of 200 g and a numberof times of friction of 10. Then, the state of the coated surface wasvisually observed by three panelists and evaluated according to criteriabelow.

G: Three panelists evaluated that no damage occurred

N: One or more panelists evaluated that damage occurred

(Marker Resistance Test)

The prepared ink was applied to PPC paper by using wire bar #3. Afternatural drying for 24 hours, a boundary between an ink coated surfaceand an uncoated surface on the coated product was traced with acommercial fluorescent pen (Text Liner manufactured by FABER-CASTELLCompany). A degree of dirt was visually observed and evaluated accordingto criteria below (three panelists).

G: By tracing with a fluorescent pen, no staining such as trailing orthe like occurred or trailing occurred at a level with no practicalproblem.

N: By tracing with a fluorescent pen, significant trailing occurred andheavy staining was observed.

<Adaptability for Ink Jet (IJ)>

With respect to discharge properties and printability, an ink jetrecording apparatus (ENVY4500 manufactured by Hewlett-Packard Company)having a thermal-type ink jet nozzle was filled with an aqueous ink in aconstant-temperature constant-humidity chamber (room temperature 25° C.,humidity 50%). Then, printing was continuously performed for 10 minuteson PPC paper as a recording material using a test print pattern (havinga character part, a ruled-line part, and a solid part). After continuousprinting for 10 minutes, the paper surface was visually observed bythree panelists and omission or blurring of the print pattern wasevaluated according to criteria below.

G: Neither omission nor blurring in the print pattern was recognized bythe three panelists.

M: Omission or blurring in the print pattern was recognized by only onepanelist (neither omission nor blurring in the print pattern wasrecognized by the other two panelists).

N: Omission or blurring in the print pattern was recognized by two ormore panelists.

The ink compositions and the ink evaluation results are shown in tablesbelow.

TABLE 4 Production Example 1 Comparative US Example Example ExampleExample Example Example Aqueous black ink (Type1) dispersion 1 2 3 4 5 1Dispersion method (US: ultrasonic US US US US US US US dispersion methodPLM: kneading method) Composition Black Product name #960 #960 #960 #960#960 #960 #960 pigment (parts) (solid 8 6 6 6 6 6 6 content) AnionicName/Product SA-1 SA-1 SA-1 SA-1 SA-1 SA-1 SA-1 group- name containing(parts) (solid 1.6 1.2 1.2 1.2 1.2 1.2 1.2 organic content) polymerName/Product — — — — — DN- — compound name 800H (parts) (solid — — — — —0.15 — content) Bio- Product name CEL-NF CEL-NF CEL-KY CEL-KY CHI-NFCHI-NF — nanofiber (abbreviation) (parts) 0.4 0.3 0.075 0.6 0.225 0.6 —Triethylene glycol (parts) 2 1.5 1.5 1.5 1.5 1.5 1.5 Pure water BalanceBalance Balance Balance Balance Balance Balance Total (parts) 100 100100 100 100 100 100 Physical pH 10.4 10.3 10.2 10.4 10.2 10.3 10.3properties Average particle 85 78 79 78 81 83 81 diameter D50/nm Initialviscosity (mPa · s) — 19.9 6.3 63.2 15.5 89.2 1.7 Optical Measured —1.43 1.38 1.44 1.42 1.44 1.34 density value Improvement — 107% 103% 107%106% 107% (reference) rate Determination — G G G G G — Rubfastness — G GG G G N

TABLE 5 Comparative Example Example Example Example Example ExampleAqueous black ink (Type1) 6 7 8 9 10 2 Dispersion method (US: ultrasonicUS US US US US US dispersion method PLM: kneading method) CompositionBlack Product name #960 #960 #960 #960 #960 #960 pigment (parts) (solid6 6 6 6 6 6 content) Anionic Name/Product UR-1 UR-1 UR-1 UR-1 UR-1 UR-1group- name containing (parts) (solid 1.2 1.2 1.2 1.2 1.2 1.2 organiccontent) polymer Name/Product — CMC DN-100L — CMC — compound name 13901390 (parts) (solid — 0.1 0.3 — 0.2 — content) Bio- Product name CHI-NFCHI-NF CHI-NF CEL-NF CEL-KY — nanofiber (abbreviation) (parts) 0.075 0.30.3 0.3 0.3 — Triethylene glycol (parts) 1.5 1.5 1.5 1.5 1.5 1.5 Purewater Balance Balance Balance Balance Balance Balance Total (parts) 100100 100 100 100 100 Physical pH 9.4 9.5 9.5 8.9 8.9 8.9 propertiesAverage particle diameter 124 123 123 110 122 125 D50/nm Initialviscosity (mPa · s) 8.2 18.2 11.6 29.5 9.8 2.3 Optical Measured 1.381.42 1.42 1.41 1.43 1.33 density value Improvement 103% 107% 107% 106%107% (reference) rate Determination G G G G G — Rubfastness G G G G G N

TABLE 6 Production Example 5 Comparative PLM Example Example ExampleExample Aqueous black ink (Type1) Dispersion 11 12 13 3 Dispersionmethod (US: ultrasonic dispersion PLM PLM PLM PLM PLM method PLM:kneading method) Composition Black pigment Product name #960 #960 #960#960 #960 (parts) (solid 8 6 6 6 6 content) Anionic Name/Product Resin AResin A Resin A Resin A Resin A group- name containing (parts) (solid1.6 1.2 1.2 1.2 1.2 organic content) polymer Name/Product — — DN-800H —— compound name (parts) (solid — — 0.15 — — content) Bio-nanofiberProduct name CHI-NF CHI-NF CHI-NF CEL-KY — (abbreviation) (parts) 0.30.225 0.225 0.6 — Triethylene glycol (parts) 8 6 6 6 6 Pure waterBalance Balance Balance Balance Balance Total (parts) 100 100 100 100100 Physical pH 9.8 9.6 10.0 10.1 10.1 properties Average particlediameter 108 104 106 111 116 D50/nm Initial viscosity (mPa · s) — 10.210.2 52.2 1.9 Optical Measured value — 1.27 1.29 1.34 1.19 densityImprovement — 107% 108% 113% (reference) rate Determination — G G G —Rubfastness — G G G N

TABLE 7 Production Example 1 US Example Example Example Example ExampleAqueous black ink (Type2) dispersion 14 15 16 17 18 Dispersion method(US: ultrasonic US US US US US US dispersion method PLM: kneadingmethod) Composition Black pigment Product name #960 #960 #960 #960 #960#960 (parts) (solid 8 4 4 4 4 4 content) Anionic Name/Product SA-1 SA-1SA-1 SA-1 SA-1 SA-1 group- name containing (parts) (solid 1.6 0.8 0.80.8 0.8 0.8 organic content) polymer Name/Product — — — — — — compoundname (parts) (solid — — — — — — content) Bio-nanofiber Product nameCEL-NF CEL-NF CEL-KY CEL-KY CEL-KY CEL-KY (abbreviation) (parts) 0.4 0.20.2 0.1 0.05 0.3 2-pyrrolidone (parts) — 8 8 8 8 8 Triethylene glycol —8 8 8 8 8 Glycerin (parts) — 3 3 3 3 3 Triethylene glycol (parts) 2 1 11 1 1 Surfynol 440(parts) — 0.5 0.5 0.5 0.5 0.5 Pure water BalanceBalance Balance Balance Balance Balance Total (parts) 100 100 100 100100 100 Physical pH 10.4 9.3 9.3 9.3 9.2 9.3 properties Average particlediameter D50/nm 85 81 82 82 83 81 Initial viscosity (mPa · s) — 3.7 16.88.8 4.5 28.1 Optical Measured value — 1.11 1.07 1.05 1.04 1.11 densityImprovement rate — 112% 108% 106% 105% 112% Determination — G G G G GRubfastness — G G G G G Maker resistance — G G G G G Ink jetadaptability — G G G G M Example Example Example Example Example ExampleAqueous black ink (Type2) 19 20 21 22 23 24 Dispersion method (US:ultrasonic US US US US US US dispersion method PLM: kneading method)Composition Black pigment Product name #960 #960 #960 #960 #960 #960(parts) (solid 4 4 4 4 4 4 content) Anionic Name/Product SA-1 SA-1 SA-1SA-1 SA-1 SA-1 group- name containing (parts) (solid 0.8 0.8 0.8 0.8 0.80.8 organic content) polymer Name/Product — CMC DN-800H CMC — — compoundname 1390 1240 (parts) (solid — 0.2 0.2 0.2 — — content) Bio-nanofiberProduct name CEL-KY CEL-KY CEL-KY CEL-KY CHI-NF CHI-NF (abbreviation)(parts) 0.4 0.2 0.2 0.2 0.05 0.15 2-pyrrolidone (parts) 8 8 8 8 8 8Triethylene glycol 8 8 8 8 8 8 Glycerin (parts) 3 3 3 3 3 3 Triethyleneglycol (parts) 1 1 1 1 1 1 Surfynol 440(parts) 0.5 0.5 0.5 0.5 0.5 0.5Pure water Balance Balance Balance Balance Balance Balance Total (parts)100 100 100 100 100 100 Physical pH 9.4 9.2 9.1 9.3 9.2 9.2 propertiesAverage particle diameter D50/nm 81 84 83 85 88 88 Initial viscosity(mPa · s) 41.3 13.7 12.0 9.6 4.8 20.1 Optical Measured value 1.15 1.081.07 1.06 1.07 1.12 density Improvement rate 116% 109% 108% 107% 108%113% Determination G G G G G G Rubfastness G G G G G G Maker resistanceG G G G G G Ink jet adaptability M G G G G M

TABLE 8 Example Example Example Example Example Example Example Aqueousblack ink (Type2) 25 26 27 28 29 30 31 Dispersion method (US: ultrasonicdispersion US US US US US US US method PLM: kneading method) CompositionBlack Product name #960 #960 #960 #960 #960 #960 #960 pigment (parts)(solid content) 4 4 4 4 4 4 4 Anionic Name/Product name SA-1 SA-1 SA-1SA-1 SA-1 SA-1 SA-1 group- (parts) (solid content) 0.8 0.8 0.8 0.8 0.80.8 0.8 containing Name/Product name DN-800H DN-100L DN-10L CMC DN-100LDN-10L DN-800H organic 1390 polymer (parts) (solid content) 0.15 0.150.15 0.1 0.2 0.1 0.3 compound Bio-nanofiber Product name CHI-NF CHI-NFCHI-NF CHI-NF CHI-NF CHI-NF CHI-NF (abbreviation) (parts) 0.15 0.15 0.150.1 0.1 0.2 0.15 2-Pyrrolidone (parts) 8 8 8 8 8 8 8 Triethylene glycol8 8 8 8 8 8 8 Glycerin (parts) 3 3 3 3 3 3 3 Triethylene glycol (parts)1 1 1 1 1 1 1 Surfynol 440 (parts) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Purewater Balance Balance Balance Balance Balance Balance Balance Total(parts) 100 100 100 100 100 100 100 Physical pH 9.4 9.5 9.4 9.2 9.2 9.27.8 properties Average particle diameter D50/nm 89 86 85 88 91 88 132Initial viscosity (mPa · s) 5.9 5.5 4.6 8.4 5.7 6.9 4.8 Optical Measuredvalue 1.09 1.07 1.04 1.10 1.09 1.10 1.07 density Improvement rate 110%108% 105% 111% 110% 111% 108% Determination G G G G G G G Rubfastness GG G G G G G Marker resistance G G G G G G G Ink jet adaptability G G G GG G G Comparative Comparative Comparative Example Example ExampleExample Example Aqueous black ink (Type2) 32 33 4 5 6 Dispersion method(US: ultrasonic dispersion US US US US US method PLM: kneading method)Composition Black Product name #960 #960 #960 #960 #960 pigment (parts)(solid content) 4 4 4 4 4 Anionic Name/Product name SA-1 SA-1 SA-1 SA-1SA-1 group- (parts) (solid content) 0.8 0.8 0.8 0.8 0.8 containingName/Product name DN-800H DN-800H CMC DN-800H — organic 1390 polymer(parts) (solid content) 0.15 0.15 0.2 0.2 — compound Bio-nanofiberProduct name CHI-NF CHI-NF — — — (abbreviation) (parts) 0.3 0.4 — — —2-Pyrrolidone (parts) 8 8 8 8 8 Triethylene glycol 8 8 8 8 8 Glycerin(parts) 3 3 3 3 3 Triethylene glycol (parts) 1 1 1 1 1 Surfynol 440(parts) 0.5 0.5 0.5 0.5 0.5 Pure water Balance Balance Balance BalanceBalance Total (parts) 100 100 100 100 100 Physical pH 9.4 9.3 9.4 9.29.3 properties Average particle diameter D50/nm 89 90 88 97 88 Initialviscosity (mPa · s) 14.2 18.8 6.7 5.1 2.3 Optical Measured value 1.141.16 1.02 1.01 0.99 density Improvement rate 115% 117% 103% 102%(Reference) Determination G G G N — Rubfastness G G N N N Markerresistance G G N N N Ink jet adaptability G M G G G

TABLE 9 Example Example Example Example Example Example Aqueous blackink (Type2) 34 35 36 37 38 39 Dispersion method (US: ultrasonic US US USUS US US dispersion method PLM: kneading method) Composition Blackpigment Product name #960 #960 #960 #960 #960 #960 (parts) (solid 4 4 44 4 4 content) Anionic group- Name/Product name UR-1 UR-1 UR-1 UR-1 UR-1UR-1 containing (parts) (solid 0.8 0.8 0.8 0.8 0.8 0.8 organic content)polymer Name/Product name — — — — CMC — compound 1390 (parts) (solid — —— — 0.2 — content) Bio-nanofiber Product name CEL-KY CEL-KY CEL-KYCEL-NF CEL-KY CHI-NF (abbreviation) (parts) 0.2 0.1 0.05 0.2 0.2 0.052-Pyrrolidone (parts) 8 8 8 8 8 8 Triethylene glycol 8 8 8 8 8 8Glycerin (parts) 3 3 3 3 3 3 Triethylene glycol (parts) 1 1 1 1 1 1Surfynol 440 (parts) 0.5 0.5 0.5 0.5 0.5 0.5 Pure water Balance BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100 100Physical pH 7.5 7.4 7.5 7.4 7.4 7.8 properties Average particle diameterD50/nm 119 124 128 117 130 132 Initial viscosity (mPa · s) 17.3 10.2 5.14.0 3.6 4.1 Optical density Measured value 1.03 1.01 0.99 1.04 1.05 1.00Improvement rate 110% 107% 105% 111% 112% 106% Determination G G G G G GRubfastness G G G G G G Maker resistance G G G G G G Ink jetadaptability G G G G G G Example Example Example Example Example ExampleAqueous black ink (Type2) 40 41 42 43 44 45 Dispersion method (US:ultrasonic US US US US US US dispersion method PLM: kneading method)Composition Black pigment Product name #960 #960 #960 #960 #960 #960(parts) (solid 4 4 4 4 4 4 content) Anionic group- Name/Product nameUR-1 UR-1 UR-1 UR-1 UR-1 UR-1 containing (parts) (solid 0.8 0.8 0.8 0.80.8 0.8 organic content) polymer Name/Product name — DN-800H DN-100LDN-10L CMC DN-100L compound 1390 (parts) (solid — 0.15 0.15 0.15 0.1 0.3content) Bio-nanofiber Product name CHI-NF CHI-NF CHI-NF CHI-NF CHI-NFCHI-NF (abbreviation) (parts) 0.15 0.15 0.15 0.15 0.2 0.2 2-Pyrrolidone(parts) 8 8 8 8 8 8 Triethylene glycol 8 8 8 8 8 8 Glycerin (parts) 3 33 3 3 3 Triethylene glycol (parts) 1 1 1 1 1 1 Surfynol 440 (parts) 0.50.5 0.5 0.5 0.5 0.5 Pure water Balance Balance Balance Balance BalanceBalance Total (parts) 100 100 100 100 100 100 Physical pH 7.8 7.9 7.87.9 7.9 7.9 properties Average particle diameter D50/nm 132 132 133 130131 131 Initial viscosity (mPa · s) 20.2 5.9 5.6 4.7 15.4 9.3 Opticaldensity Measured value 1.03 1.06 1.07 1.02 1.08 1.08 Improvement rate110% 113% 114% 109% 115% 115% Determination G G G G G G Rubfastness G GG G G G Maker resistance G G G G G G Ink jet adaptability M G G G M G

TABLE 10 Production Comparative Comparative Example 5 Example ExampleExample PLM Example Example Aqueous black ink (Type2) 46 7 8 Dispersion47 48 Dispersion method (US: ultrasonic dispersion method US US US PLMPLM PLM PLM: kneading method) Composition Black Product name #960 #960#960 #960 #960 #960 pigment (parts) (solid content) 4 4 4 8 4 4 AnionicName/Product name UR-1 UR-1 UR-1 Resin A Resin A Resin A group- (parts)(solid content) 0.8 0.8 0.8 1.6 0.8 0.8 containing Name/Product name DN-CMC — — — — organic 800H 1390 polymer (parts) (solid content) 0.15 0.2 —— — — compound Bio- Product name- CHI-NF CHI-NF CHI-NF CEL-KY nanofiberabbreviation (parts) 0.4 — — 0.3 0.15 0.2 2-Pyrrolidone (parts) 8 8 8 —8 8 Triethylene glycol 8 8 8 — 8 8 Glycerin (parts) 3 3 3 — 3 3Triethylene glycol (parts) 1 1 1 8 4 4 Surfynol 440(parts) 0.5 0.5 0.5 —0.5 0.5 Pure water Balance Balance Balance Balance Balance Balance Total(parts) 100 100 100 100 100 100 Physical pH 8.0 7.3 7.4 9.8 9.0 9.5properties Average particle diameter D50/nm 138 91 133 108 87 96 Initialviscosity (mPa · s) 18.5 4.2 14.5 — 20.2 7.3 Optical Measured value 1.090.96 0.94 — 1.05 1.01 density Improvement rate 116% 102% (Reference) —112% 107% Determination G N — — G G Rubfastness G N N — G G Makerresistance G N N — G G Ink jet adaptability M G G — M G Example ExampleExample Example Example Example Aqueous black ink (Type2) 49 50 51 52 5354 Dispersion method (US: ultrasonic dispersion method PLM PLM PLM PLMPLM PLM PLM: kneading method) Composition Black Product name #960 #960#960 #960 #960 #960 pigment (parts) (solid content) 4 4 4 4 4 4 AnionicName/Product name Resin A Resin A Resin A Resin A Resin A Resin A group-(parts) (solid content) 0.8 0.8 0.8 0.8 0.8 0.8 containing Name/Productname — — — — — CMC organic 1390 polymer (parts) (solid content) — — — —— 0.2 compound Bio- Product name- CEL-KY CEL-KY CEL-KY CEL-KY CEL-NFCEL-KY nanofiber abbreviation (parts) 0.1 0.05 0.3 0.4 0.2 0.22-Pyrrolidone (parts) 8 8 8 8 8 8 Triethylene glycol 8 8 8 8 8 8Glycerin (parts) 3 3 3 3 3 3 Triethylene glycol (parts) 4 4 4 4 4 4Surfynol 440(parts) 0.5 0.5 0.5 0.5 0.5 0.5 Pure water Balance BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100 100Physical pH 9.5 9.4 9.4 9.5 9.5 9.4 properties Average particle diameterD50/nm 96 97 95 93 92 94 Initial viscosity (mPa · s) 4.8 3.2 16.8 29.34.5 6.9 Optical Measured value 1.00 0.99 1.04 1.10 1.05 1.01 densityImprovement rate 106% 105% 111% 117% 112% 107% Determination G G G G G GRubfastness G G G G G G Maker resistance G G G G G G Ink jetadaptability G G M M G G

TABLE 11 Example Example Example Example Example Aqueous black ink(Type2) 55 56 57 58 59 Dispersion method (US: ultrasonic dispersionmethod PLM PLM PLM PLM PLM PLM: kneading method) Composition Blackpigment Product name #960 #960 #960 #960 #960 (parts) (solid content) 44 4 4 4 Anionic group-containing Name/Product name Resin A Resin A ResinA Resin A Resin A organic polymer compound (parts) (solid content) 0.80.8 0.8 0.8 0.8 Name/Product name DN-800H DN-800H DN-100L DN-10L CMC1390 (parts) (solid content) 0.2 0.15 0.15 0.15 0.1 Bio-nanofiberProduct name- CEL-KY CHI-NF CHI-NF CHI-NF CHI-NF abbreviation (parts)0.2 0.15 0.15 0.15 0.15 2-Pyrrolidone (parts) 8 8 8 8 8 Triethyleneglycol 8 8 8 8 8 Glycerin (parts) 3 3 3 3 3 Triethylene glycol (parts) 44 4 4 4 Surfynol 440(parts) 0.5 0.5 0.5 0.5 0.5 Pure water BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100Physical properties pH 9.3 9.4 9.4 9.5 9.4 Average particle diameterD50/nm 95 89 89 87 85 Initial viscosity (mPa · s) 5.9 6.0 5.6 4.7 15.5Optical density Measured value 1.00 1.08 1.02 1.01 1.05 Improvement rate106% 115% 109% 107% 112% Determination G G G G G Rubfastness G G G G GMaker resistance G G G G G Ink jet adaptability G G G G M ComparativeComparative Comparative Example Example Example Example Aqueous blackink (Type2) 60 9 10 11 Dispersion method (US: ultrasonic dispersionmethod PLM PLM PLM PLM PLM: kneading method) Composition Black pigmentProduct name #960 #960 #960 #960 (parts) (solid content) 4 4 4 4 Anionicgroup-containing Name/Product name Resin A Resin A Resin A Resin Aorganic polymer compound (parts) (solid content) 0.8 0.8 0.8 0.8Name/Product name DN-800H CMC DN-800H — 1390 (parts) (solid content)0.15 0.2 0.2 — Bio-nanofiber Product name- CHI-NF — — — abbreviation(parts) 0.4 — — — 2-Pyrrolidone (parts) 8 8 8 8 Triethylene glycol 8 8 88 Glycerin (parts) 3 3 3 3 Triethylene glycol (parts) 4 4 4 4 Surfynol440(parts) 0.5 0.5 0.5 0.5 Pure water Balance Balance Balance BalanceTotal (parts) 100 100 100 100 Physical properties pH 9.5 9.6 9.4 9.5Average particle diameter D50/nm 97 97 103 97 Initial viscosity (mPa ·s) 18.6 4.2 3.9 2.8 Optical density Measured value 1.15 0.97 0.97 0.94Improvement rate 122% 103% 103% (Reference) Determination G G G —Rubfastness G N N N Maker resistance G N N N Ink jet adaptability M G GG

TABLE 12 Comparative Comparative Example Example Example Example ExampleExample Aqueous black ink (Type2) 61 62 63 64 12 13 Dispersion method(US: ultrasonic dispersion method Self- Self- Self- Self-Self-dispersion Self- PLM: kneading method) dispersion dispersiondispersion dispersion type dispersion type type type type typeComposition Black pigment Product name CAB-O- CAB-O- CAB-O- CAB-O-CAB-O- CAB-O- JET JET JET JET JET JET 400 400 400 400 400 400 (parts)(solid content) 4 4 4 4 4 4 Anionic group- Name/Product name — — — — — —containing organic (parts) (solid content) — — — — — — polymerName/Product name CMC DN-800H CMC DN-800H — DN-800H compound 1390 1390(parts) (solid content) 0.2 0.2 0.2 0.2 — 0.2 Bio-nanofiber Productname- CEL-NF CEL-NF CEL-KY CEL-KY CEL-NF — abbreviation (parts) 0.2 0.20.2 0.2 0.5 — 2-Pyrrolidone (parts) 8 8 8 8 8 8 Triethylene glycol 8 8 88 8 8 Glycerin (parts) 3 3 3 3 3 3 Triethylene glycol (parts) 1 1 1 1 11 Surfynol 440(parts) 0.5 0.5 0.5 0.5 0.5 0.5 Pure water Balance BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100 100Physical pH 8.3 8.0 8.2 8.1 8.4 8.2 properties Average particle diameterD50/nm 131 148 131 139 386 139 Initial viscosity (mPa · s) 6.6 4.9 8.37.2 88.3 6.9 Optical density Measured value 1.32 1.29 1.22 1.20 1.581.10 Improvement rate 126% 123% 116% 114% 150% 105% Determination G G GG G G Rubfastness G G G G G N Maker resistance G G G G G N Ink jetadaptability G G G G N G Comparative Comparative Example Example ExampleExample Aqueous black ink (Type2) 14 65 66 12 Dispersion method (US:ultrasonic dispersion method Self-dispersion Self- Self- Self- PLM:kneading method) type dispersion dispersion dispersion type type typeComposition Black pigment Product name CAB-O- SENSI SENSI SENSI JET JETBlack JET Black JET Black 400 SDP SDP SDP 100 100 100 (parts) (solidcontent) 4 4 4 4 Anionic group- Name/Product name — — — — containingorganic (parts) (solid content) — — — — polymer Name/Product name — CMCCMC — compound 1390 1390 (parts) (solid content) — 0.2 0.2 —Bio-nanofiber Product name- — CEL-NF CEL-KY — abbreviation (parts) — 0.20.2 — 2-Pyrrolidone (parts) 8 8 8 8 Triethylene glycol 8 8 8 8 Glycerin(parts) 3 3 3 3 Triethylene glycol (parts) I 1 1 1 Surfynol 440(parts)0.5 0.5 0.5 0.5 Pure water Balance Balance Balance Balance Total (parts)100 100 100 100 Physical pH 8.3 8.1 8.1 7.9 properties Average particlediameter D50/nm 131 118 121 117 Initial viscosity (mPa · s) 2.1 8.8 8.82.1 Optical density Measured value 1.05 1.29 1.25 1.15 Improvement rate(Reference) 112% 109% (Reference) Determination — G G — Rubfastness N GG N Maker resistance N G G N Ink jet adaptability G G G G

TABLE 13 Production Example 2 US Example Example Example Example ExampleAqueous cyan ink (Type1) Dispersion 67 68 69 70 71 Dispersion method(US: ultrasonic dispersion US US US US US US method PLM: kneadingmethod) Composition Cyan pigment Product name FASTOGEN FASTOGEN FASTOGENFASTOGEN FASTOGEN FASTOGEN Blue TGR Blue TGR Blue TGR Blue TGR Blue TGRBlue TGR (parts) (solid 8 6 6 6 6 6 content) Anionic group- Name/ProductSA-1 SA-1 SA-1 SA-1 SA-1 SA-1 containing name organic polymer (parts)(solid 1.6 1.2 1.2 1.2 1.2 1.2 compound content) Name/Product — — — —CMC DN-800H name 1390 (parts) (solid — — — — 0.3 0.225 content)Bio-nanofiber Product name CHI-NF CHI-NF CEL-KY CEL-NF CEL-NF CHI-NF(abbreviation) (parts) (solid 0.1 0.075 0.3 0.15 0.3 0.6 content)Triethylene glycol (parts) 8 6 6 6 6 6 Pure water Balance BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100 100Physical pH 9.6 9.4 9.5 9.6 9.5 9.6 properties Average particle diameterD50/nm 96 93 94 93 94 91 Initial viscosity (mPa · s) — 3.9 13.8 5.2 18.163.4 Optical density Measured value — 1.27 1.26 1.23 1.28 1.36Improvement rate — 108% 107% 105% 109% 115% Determination — G G G G GRubfastness — G G G G G Comparative Comparative Example Example ExampleExample Example Example Aqueous cyan ink (Type1) 13 72 73 74 75 14Dispersion method (US: ultrasonic dispersion US US US US US US methodPLM: kneading method) Composition Cyan pigment Product name FASTOGENFASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN Blue TGR Blue TGR Blue TGRBlue TGR Blue TGR Blue TGR (parts) (solid 6 6 6 6 6 6 content) Anionicgroup- Name/Product SA-1 UR-1 UR-1 UR-1 UR-1 UR-1 containing nameorganic polymer (parts) (solid 1.2 1.2 1.2 1.2 1.2 1.2 compound content)Name/Product — — DN-800H DN-100L — — name (parts) (solid — — 0.225 0.225— — content) Bio-nanofiber Product name CHI-NF CHI-NF CHI-NF CEL-KY(abbreviation) (parts) (solid — 0.225 0.225 0.6 0.3 — content)Triethylene glycol (parts) 6 6 6 6 6 6 Pure water Balance BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100 100Physical pH 9.6 8.9 8.8 8.9 8.9 9.6 properties Average particle diameterD50/nm 91 120 125 121 99 91 Initial viscosity (mPa · s) 1.8 6.2 9.4 59.119.3 2.4 Optical density Measured value 1.17 1.23 1.28 1.34 1.21 1.09Improvement rate (Reference) 113% 118% 123% 111% (Reference)Determination — G G G G — Rubfastness N G G G G N

TABLE 14 Production Example 6 Comparative PLM Example Example ExampleExample Aqueous cyan ink (Type1) Dispersion 76 77 15 78 Dispersionmethod (US: ultrasonic dispersion method PLM PLM PLM PLM Self- PLM:kneading method) dispersion type Composition Cyan pigment Product nameFASTOGEN FASTOGEN FASTOGEN FASTOGEN CAB-O-JET Blue TGR Blue TGR Blue TGRBlue TGR 450C (parts) (solid content) 8 6 6 6 6 Anionic group-containingName/Product name Resin A Resin A Resin A Resin A — organic polymer(parts) (solid content) 2.4 1.8 1.8 1.8 — compound Name/Product nameDN-800H DN-800H DN-800H — CMC 1390 (parts) (solid content) 0.4 0.3 0.225— 0.3 Bio-nanofiber Product name CHI-NF CHI-NF CHI-NF CEL-NF(abbreviation) (parts) (solid content) 0.3 0.225 0.6 — 0.3 Triethyleneglycol (parts) 3 2.25 2.25 2.25 1.5 Pure water Balance Balance BalanceBalance Balance Total (parts) 100 100 100 100 100 Physical pH 9.9 9.89.9 9.9 9.8 properties Average particle diameter D50/nm 95 90 95 89 86Initial viscosity (mPa · s) — 13.6 52.8 1.5 35.1 Optical densityMeasured value — 1.25 1.32 1.16 1.39 Improvement rate — 107% 114%(Reference) 115% Determination — G G — G Rubfastness — G G N GComparative Example Example Example Example Aqueous cyan ink (Type1) 7980 81 16 Dispersion method (US: ultrasonic dispersion method Self- Self-Self- Self- PLM: kneading method) dispersion dispersion dispersiondispersion type type type type Composition Cyan pigment Product nameCAB-O-JET CAB-O-JET CAB-O- CAB-O-JET 450C 450C JET 450C 450C (parts)(solid content) 6 6 6 6 Anionic group-containing Name/Product name — — —— organic polymer (parts) (solid content) — — — — compound Name/Productname DN-800H CMC DN-800H — 1390 (parts) (solid content) 0.3 0.3 0.3 —Bio-nanofiber Product name CEL-NF CEL-KY CEL-KY (abbreviation) (parts)(solid content) 0.3 0.3 0.3 — Triethylene glycol (parts) 1.5 1.5 1.5 1.5Pure water Balance Balance Balance Balance Total (parts) 100 100 100 100Physical pH 9.4 9.8 9.5 9.7 properties Average particle diameter D50/nm83 89 90 84 Initial viscosity (mPa · s) 15.2 23.5 9.9 1.2 Opticaldensity Measured value 1.34 1.29 1.28 1.21 Improvement rate 111% 107%106% (Reference) Determination G G G — Rubfastness G G G N

TABLE 15 Production Example 2 US Example Example Example Example ExampleAqueous cyan ink (Type2) Dispersion 82 83 84 85 86 Dispersion method(US: ultrasonic dispersion US US US US US US method PLM: kneadingmethod) Composition Cyan pigment Product name FASTOGEN FASTOGEN FASTOGENFASTOGEN FASTOGEN FASTOGEN Blue TGR Blue TGR Blue TGR Blue TGR Blue TGRBlue TGR (parts) (solid 8 4 4 4 4 4 content) Anionic Name/Product nameSA-1 SA-1 SA-1 SA-1 SA-1 SA-1 group- (parts) (solid 1.6 0.8 0.8 0.8 0.80.8 containing content) organic Name/Product name — — — — CMC DN-800Hpolymer 1390 compound (parts) (solid — — — — 0.2 0.2 content)Bio-nanofiber Product name CHI-NF CHI-NF CEL-KY CEL-KY CEL-KY CEL-KY(abbreviation) (parts) (solid 0.1 0.05 0.2 0.1 0.2 0.2 content)2-Pyrrolidone (parts) — 8 8 8 8 8 Triethylene glycol — 8 8 8 8 8Glycerin (parts) — 3 3 3 3 3 Triethylene glycol (parts) 8 4 4 4 4 4Surfynol 440(parts) — 0.5 0.5 0.5 0.5 0.5 Pure water Balance BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100 100Physical pH 9.6 8.8 8.9 9.0 8.9 8.9 properties Average particle diameterD50/nm 96 95 96 95 96 96 Initial viscosity (mPa · s) — 4.5 9.7 5.1 8.89.7 Optical Measured value — 1.05 1.04 1.02 1.06 1.04 densityImprovement rate — 108% 107% 105% 109% 107% Determination — G G G G GRubfastness — G G G G G Ink jet adaptability — G G G G G Example ExampleExample Example Example Example Aqueous cyan ink (Type2) 87 88 89 90 9192 Dispersion method (US: ultrasonic dispersion US US US US US US methodPLM: kneading method) Composition Cyan pigment Product name FASTOGENFASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN Blue TGR Blue TGR Blue TGRBlue TGR Blue TGR Blue TGR (parts) (solid 4 4 4 4 4 4 content) AnionicName/Product name SA-1 SA-1 SA-1 SA-1 SA-1 SA-1 group- (parts) (solid0.8 0.8 0.8 0.8 0.8 0.8 containing content) organic Name/Product name —DN-800H DN-10L DN-100L CMC DN-100L polymer 1390 compound (parts) (solid— 0.15 0.15 0.2 0.1 0.15 content) Bio-nanofiber Product name CHI-NFHI-NF CHI-NF CHI-NF CHI-NF CHI-NF (abbreviation) (parts) (solid 0.150.15 0.15 0.1 0.15 0.3 content) 2-Pyrrolidone (parts) 8 8 8 8 8 8Triethylene glycol 8 8 8 8 8 8 Glycerin (parts) 3 3 3 3 3 3 Triethyleneglycol (parts) 4 4 4 4 4 4 Surfynol 440(parts) 0.5 0.5 0.5 0.5 0.5 0.5Pure water Balance Balance Balance Balance Balance Balance Total (parts)100 100 100 100 100 100 Physical pH 8.8 9.2 9.3 9.0 9.0 9.0 propertiesAverage particle diameter D50/nm 95 92 93 95 95 95 Initial viscosity(mPa · s) 16.8 7.9 7.8 8.3 15.2 11.7 Optical Measured value 1.10 1.071.05 1.08 1.08 1.10 density Improvement rate 113% 110% 108% 111% 111%113% Determination G G G G G G Rubfastness G G G G G G Ink jetadaptability M G G G M G

TABLE 16 Comparative Example Example Example Example Example Aqueouscyan ink (Type2) 93 17 94 95 96 Dispersion method (US: ultrasonicdispersion method US US US US US PLM: kneading method) Composition Cyanpigment Product name FASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN BlueTGR Blue TGR Blue TGR Blue TGR Blue TGR (parts) (solid content) 4 4 4 44 Anionic group-containing Name/Product name SA-1 SA-1 UR-1 UR-1 UR-1organic polymer compound (parts) (solid content) 0.8 0.8 0.8 0.8 0.8Name/Product name DN-800H — — — DN-800H (parts) (solid content) 0.15 — —— 0.15 Bio-nanofiber Product name CHI-NF — CEL-KY CHI-NF CHI-NF(abbreviation) (parts) (solid content) 0.4 — 0.2 0.15 0.15 2-Pyrrolidone(parts) 8 8 8 8 8 Triethylene glycol 8 8 8 8 8 Glycerin (parts) 3 3 3 33 Triethylene glycol (parts) 4 4 4 4 4 Surfynol 440(parts) 0.5 0.5 0.50.5 0.5 Pure water Balance Balance Balance Balance Balance Total (parts)100 100 100 100 100 Physical pH 9.0 9.0 8.3 8.3 8.2 properties Averageparticle diameter D90/nm 93 93 101 122 127 Initial viscosity (mPa · s)17.3 2.1 8.9 7.7 18.8 Optical density Measured value 1.12 0.97 1.00 1.021.06 Improvement rate 115% (Reference) 111% 113% 118% Determination G —G G G Rubfastness G N G G G Ink jet adaptability M G G G M ComparativeExample Example Example Example Aqueous cyan ink (Type2) 97 98 99 18Dispersion method (US: ultrasonic dispersion method US US US US PLM:kneading method) Composition Cyan pigment Product name FASTOGEN FASTOGENFASTOGEN FASTOGEN Blue TGR Blue TGR Blue TGR Blue TGR (parts) (solidcontent) 4 4 4 4 Anionic group-containing Name/Product name UR-1 UR-1UR-1 UR-1 organic polymer compound (parts) (solid content) 0.8 0.8 0.80.8 Name/Product name DN-10L CMC DN-100L — 1390 (parts) (solid content)0.15 0.1 0.15 — Bio-nanofiber Product name CHI-NF CHI-NF CHI-NF —(abbreviation) (parts) (solid content) 0.15 0.15 0.4 — 2-Pyrrolidone(parts) 8 8 8 8 Triethylene glycol 8 8 8 8 Glycerin (parts) 3 3 3 3Triethylene glycol (parts) 4 4 4 4 Surfynol 440(parts) 0.5 0.5 0.5 0.5Pure water Balance Balance Balance Balance Total (parts) 100 100 100 100Physical pH 8.4 8.3 8.3 9.0 properties Average particle diameter D90/nm121 122 123 93 Initial viscosity (mPa · s) 12.4 5.8 17.1 2.5 Opticaldensity Measured value 1.04 1.01 1.11 0.90 Improvement rate 116% 112%123% (Reference) Determination G G G — Rubfastness G G G N Ink jetadaptability G G M G

TABLE 17 Production Example 6 Comparative Comparative PLM ExampleExample Example Example Example Example Example Example Example ExampleExample Aqueous cyan ink (Type2) Dispersion 100 101 102 103 104 105 106107 108 19 20 Dispersion method (US: ultrasonic dispersion PLM PLM PLMPLM PLM PLM PLM PLM PLM PLM PLM PLM method PLM: kneading method)Composition Cyan Product name FASTOGEN FASTOGEN FASTOGEN FASTOGENFASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGENpigment Blue TGR Blue TGR Blue TGR Blue TGR Blue TGR Blue TGR Blue TGRBlue TGR Blue TGR Blue TGR Blue TGR Blue TGR (parts) (solid 8 4 4 4 4 44 4 4 4 4 4 content) Anionic Name/Product Resin A Resin A Resin A ResinA Resin A Resin A Resin A Resin A Resin A Resin A Resin A Resin A group-name containing (parts) (solid 2.4 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.21.2 1.2 organic content) polymer Name/Product DN-800H DN-800H — —DN-800H CMC DN-100L CMC DN-100L DN-800H DN-800H — compound name 13901390 (parts) (solid 0.4 0.2 — — 0.2 0.1 0.15 0.1 0.15 0.15 0.2 —content) Bio- Product name CHI-NF CHI-NF CEL-KY CEL-KY CEL-KY CEL-KYCHI-NF CHI-NF CHI-NF CHI-NF — — nanofiber (abbreviation) (parts) (solid0.3 0.15 0.2 0.1 0.2 0.1 0.2 0.15 0.3 0.4 — — content) 2-Pyrrolidone(parts) — 8 8 8 8 8 8 8 8 8 8 8 Triethylene glycol — 8 8 8 8 8 8 8 8 8 88 Glycerin (parts) — 3 3 3 3 3 3 3 3 3 3 3 Triethylene glycol (parts) 31.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Surfynol 440(parts) — 0.50.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Pure water Balance BalanceBalance Balance Balance Balance Balance Balance Balance Balance BalanceBalance Total (parts) 100 100 100 100 100 100 100 100 100 100 100 100Physical pH 9.9 9.2 9.3 9.3 9.1 9.1 9.3 9.0 8.8 9.3 9.1 9.3 propertiesAverage particle 95 92 92 92 93 93 93 96 96 97 90 91 diameter D50/nmInitial viscosity (mPa · s) — 9.9 6.6 3.9 25.6 14.8 7.9 9.1 16.1 17.412.8 2.5 Optical Measured value — 1.03 1.00 0.98 0.99 0.99 1.02 1.011.06 1.09 0.97 0.95 density Improvement rate — 108% 105% 103% 104% 104%107% 106% 112% 115% 102% (Reference) Determination — G G G G G G G G G N— Rubfastness — G G G G G G G G G N N Ink jet adaptability — G G G M G GG M M G G

TABLE 18 Comparative Comparative Comparative Example Example ExampleExample Example Example Example Aqueous cyan ink (Type 2) 109 110 111112 21 22 23 Dispersion method (US: ultrasonic dispersion method Self-Self- Self- Self- Self- Self- Self- PLM: kneading method) dispersiondispersion dispersion dispersion dispersion dispersion dispersion typetype type type type type type Composition Cyan pigment Product nameCAB-O- CAB-O- CAB-O- CAB-O- CAB-O- CAB-O- CAB-O- JET JET JET JET JET JETJET 450C 450C 450C 450C 450C 450C 450C (parts) (solid content) 4 4 4 4 44 4 Anionic Name/Product name — — — — — — — group-containing (parts)(solid content) — — — — — — — organic polymer Name/Product name CMCDN-800H CMC DN-800H — CMC — compound 1390 1390 1390 (parts) (solidcontent) 0.2 0.2 0.2 0.2 — 0.2 — Bio-nanofiber Product name CEL-NFCEL-NF CEL-KY CEL-KY CEL-NF — — (abbreviation) (parts) (solid content)0.2 0.2 0.2 0.2 0.5 — — 2-Pyrrolidone (parts) 8 8 8 8 8 8 8 Triethyleneglycol 8 8 8 8 8 8 8 Glycerin (parts) 3 3 3 3 3 3 3 Triethylene glycol(parts) 1 1 1 1 1 1 1 Surfynol 440 (parts) 0.5 0.5 0.5 0.5 0.5 0.5 0.5Pure water Balance Balance Balance Balance Balance Balance Balance Total(parts) 100 100 100 100 100 100 100 Physical pH 9.2 8.8 9.2 8.9 9.2 9.09.1 properties Average particle diameter D50/nm 88 85 91 92 203 86 86Initial viscosity (mPa · s) 13.4 9.7 10.7 9.9 456.0 6.9 2.0 Opticaldensity Measured value 1.15 1.11 1.07 1.06 1.40 1.01 1.00 Improvementrate 115% 111% 107% 106% 140% 101% (Reference) Determination G G G G G N— Rubfastness G G G G G N N Ink jet adaptability M G G G N G G

TABLE 19 Production Example 3 Example Example Example Example Aqueousmagenta ink (Type 1) US Dispersion 113 114 115 116 Dispersion method(US: ultrasonic dispersion US US US US US method) Composition MagentaProduct name FASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN pigment SuperMagenta Super Magenta Super Magenta Super Magenta Super Magenta RY RY RYRY RY (parts) (solid 8 6 6 6 6 content) Anionic group- Name/Product SA-1SA-1 SA-1 SA-1 SA-1 containing name organic (parts) (solid 2.4 1.8 1.81.8 1.8 polymer content) compound Name/Product — — — CMC DN-800H name1390 (parts) (solid — — — 0.3 0.3 content) Bio-nanofiber Product nameCHI- CHI- CEL- CEL-NF CEL-KY (abbreviation) NF NF NF (parts) (solid 0.10.075 0.15 0.15 0.15 content) Triethylene glycol (parts) 8 6 6 6 6 Purewater Balance Balance Balance Balance Balance Total (parts) 100 100 100100 100 Physical pH 9.9 9.6 9.9 10.0 10.0 properties Average particlediameter D50/nm 96 90 105 105 104 Initial viscosity (mPa · s) — 3.1 34.511.7 17.1 Optical density Measured value — 1.20 1.19 1.35 1.32Improvement rate — 104% 103% 117% 115% Determination — G G G GRubfastness — G G G G Comparative Comparative Example Example ExampleExample Example Aqueous magenta ink (Type 1) 117 24 118 119 25Dispersion method (US: ultrasonic dispersion US US US US US method)Composition Magenta Product name FASTOGEN FASTOGEN FASTOGEN FASTOGENFASTOGEN pigment Super Magenta Super Magenta Super Magenta Super MagentaSuper Magenta RY RY RY RY RY (parts) (solid 6 6 6 6 6 content) Anionicgroup- Name/Product SA-1 SA-1 UR-1 UR-1 UR-1 containing name organic(parts) (solid 1.8 1.8 1.8 1.8 1.8 polymer content) compoundName/Product DN-800H — DN-10L DN-100L — name (parts) (solid 0.225 — 0.150.225 — content) Bio-nanofiber Product name CHI-NF — CHI-NF CHI-NF —(abbreviation) (parts) (solid 0.6 — 0.225 0.6 — content) Triethyleneglycol (parts) 6 6 6 6 6 Pure water Balance Balance Balance BalanceBalance Total (parts) 100 100 100 100 100 Physical pH 9.8 10.1 9.3 9.28.6 properties Average particle diameter D50/nm 94 104 96 103 105Initial viscosity (mPa · s) 49.3 1.4 11.6 56.6 2.3 Optical densityMeasured value 1.34 1.15 1.16 1.19 1.07 Improvement rate 117%(Reference) 109% 111% (Reference) Determination G — G G — Rubfastness GN G G G

TABLE 20 Production Example 7 Comparative PLM Example Example ExampleExample Example Aqueous magenta ink (Type 1) Dispersion 120 121 122 12326 Dispersion method (US: ultrasonic dispersion method PLM PLM PLM PLMPLM PLM PLM: kneading method) Composition Magenta pigment Product nameFASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN Super Super SuperSuper Super Super Magenta RY Magenta RY Magenta RY Magenta RY Magenta RYMagenta RY (parts) (solid content) 8 6 6 6 6 6 Anionic Name/Product nameResin A Resin A Resin A Resin A Resin A Resin A group-containing (parts)(solid content) 1.6 1.2 1.2 1.2 1.2 1.2 organic polymer Name/Productname — — CMC DN-100L CMC — compound 1390 1390 (parts) (solid content) —— 0.15 0.225 0.15 — Bio-nanofiber Product name CEL-KY CEL-KY CEL-NFCHI-NF CHI-NF — (abbreviation) (parts) (solid content) 0.2 0.15 0.15 0.30.225 — Triethylene glycol (parts) 5.4 4.05 4.05 4.05 4.05 4.05 Purewater Balance Balance Balance Balance Balance Balance Total (parts) 100100 100 100 100 100 Physical pH 10.3 10.0 10.0 10.1 9.8 10.0 propertiesAverage particle diameter D50/nm 101 96 98 88 91 101 Initial viscosity(mPa · s) — 47.8 27.6 9.5 5.0 1.5 Optical density Measured value — 1.161.17 1.20 1.19 1.12 Improvement rate — 104% 104% 107% 106% (Reference)Determination — G G G G — Rubfastness — G G G G N

TABLE 21 Compara- Compara- tive tive Comparative Example Example ExampleExample Example Example Example Aqueous magenta ink (Type 1) 124 125 126127 27 28 29 Dispersion method (US: ultrasonic dispersion method Self-Self- Self- Self- Self- Self- Self- PLM: kneading method) dispersiondispersion dispersion dispersion dispersion dispersion dispersion typetype type type type type type Composition Magenta pigment Product nameCAB- CAB- CAB- CAB- CAB- CAB- CAB-O-JET O-JET O-JET O-JET O-JET O-JETO-JET 465M 465M 465M 465M 465M 465M 465M (parts) (solid content) 6 6 6 66 6 6 Anionic group-containing Name/Product name — — — — — — — organicpolymer (parts) (solid content) — — — — — — — compound Name/Product nameCMC DN-800H CMC DN-800H DN-800H — — 1390 1390 (parts) (solid content)0.3 0.3 0.3 0.3 0.3 — — Bio-nanofiber Product name CEL-NF CEL-NF CEL-KYCEL-KY — CEL-NF — (abbreviation) (parts) (solid content) 0.3 0.3 0.3 0.3— 0.75 — Triethylene glycol (parts) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Purewater Balance Balance Balance Balance Balance Balance Balance Total(parts) 100 100 100 100 100 100 100 Physical pH 9.5 9.3 9.7 9.7 9.5 10.09.7 properties Average particle diameter D50/nm 74 69 75 71 84 193 73Initial viscosity (mPa · s) 24.1 18.2 20.9 16.5 5.5 158.0 2.4 Opticaldensity Measured value 1.37 1.31 1.16 1.15 1.10 1.65 1.08 Improvementrate 127% 121% 107% 106% 101% 152% (Reference) Determination G G G G N G— Rubfastness G G G G N N N

TABLE 22 Production Example 3 US Example Example Example Example Aqueousmagenta ink (Type 2) Dispersion 128 129 130 131 Dispersion method (US:ultrasonic dispersion method) US US US US US Composition Magenta pigmentProduct name FASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN Super SuperSuper Super Super Magenta RY Magenta RY Magenta RY Magenta RY Magenta RY(parts) (solid content) 8 4 4 4 4 Anionic: group- Name/Product name SA-1SA-1 SA-1 SA-1 SA-1 containing organic (parts) (solid content)   2.4  1.2   1.2   1.2   1.2 polymer compound Name/Product name — — — —CMC1390 (parts) (solid content) — — — —   0.2 Bio-nanofiber Product nameCHI-NF CHI-NF CEL-KY CEL-KY CEL-KY (abbreviation) (parts) (solidcontent)   0.1   0.05   0.2   0.1   0.1 2-Pyrrolidone (parts) — 8 8 8 8Triethylene glycol — 8 8 8 8 Glycerin (parts) — 3 3 3 3 Triethyleneglycol (parts) 8 4 4 4 4 Surfynol 440 (parts) —   0.5   0.5   0.5   0.5Pure water Balance Balance Balance Balance Balance Total (parts) 100 100  100  100  100  Physical pH   9.9   8.8   9.0   9.1   9.2 propertiesAverage particle diameter D50/nm 96  95  102  110  110  Initialviscosity (mPa · s) —   3.3  16.2  10.9  13.2 Optical density Measuredvalue —   0.91   0.97   0.96   0.98 Improvement rate — 105% 111% 110%113% Determination — G G G G Rubfastness — G G G G Ink jet adaptability— G M G G Example Example Example Example Example Aqueous magenta ink(Type 2) 132 133 134 135 136 Dispersion method (US: ultrasonicdispersion method) US US US US US Composition Magenta pigment Productname FASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN Super Super SuperSuper Super Magenta RY Magenta RY Magenta RY Magenta RY Magenta RY(parts) (solid content) 4 4 4 4 4 Anionic: group- Name/Product name SA-1SA-1 SA-1 SA-1 SA-1 containing organic (parts) (solid content)   1.2  1.2   1.2   1.2   1.2 polymer compound Name/Product name DN-800H —DN-800H DN-100L DN-10L (parts) (solid content)   0.2 —   0.15   0.2  0.1 Bio-nanofiber Product name CEL-KY CHI-NF CHI-NF CHI-NF CHI-NF(abbreviation) (parts) (solid content)   0.1   0.15   0.15   0.2   0.22-Pyrrolidone (parts) 8 8 8 8 8 Triethylene glycol 8 8 8 8 8 Glycerin(parts) 3 3 3 3 3 Triethylene glycol (parts) 4 4 4 4 4 Surfynol 440(parts)   0.5   0.5   0.5   0.5   0.5 Pure water Balance Balance BalanceBalance Balance Total (parts) 100  100  100  100  100  Physical pH   9.2  8.8   9.2   9.3   9.0 properties Average particle diameter D50/nm 109 95  92  93  95  Initial viscosity (mPa · s)   9.8  16.1   9.1   9.3  7.2 Optical density Measured value   0.98   0.92   0.92   0.94   0.91Improvement rate 113% 106% 106% 108% 105% Determination G G G G GRubfastness G G G G G Ink jet adaptability G M G G G

TABLE 23 Comparative Example Example Example Example Example Aqueousmagenta ink (Type 2) 137 138 30 139 140 Dispersion method (US:ultrasonic dispersion method) US US US US US Composition Magenta pigmentProduct name FASTOGEN FASTOGEN FASTOGEN FASTOGEN FASTOGEN Super SuperSuper Super Super Magenta RY Magenta RY Magenta RY Magenta RY Magenta RY(parts) (solid content) 4 4 4 4 4 Anionic group- Name/Product name SA-1SA-1 SA-1 UR-1 UR-1 containing organic (parts) (solid content)   1.2  1.2   1.2   1.2   1.2 polymer compound Name/Product name DN-100LDN-800H — — — (parts) (solid content)   0.15   0.15 — — — Bio-nanofiberProduct name CHI-NF CHI-NF — CEL-KY CHI-NF (abbreviation) (parts) (solidcontent)   0.25   0.4 —   0.1   0.15 2-Pyrrolidone (parts) 8 8 8 8 8Triethylene glycol 8 8 8 8 8 Glycerin (parts) 3 3 3 3 3 Triethyleneglycol (parts) 4 4 4 4 4 Surfynol 440 (parts)   0.5   0.5   0.5   0.5  0.5 Pure water Balance Balance Balance Balance Balance Total (parts)100  100  100  100  100  Physical pH   8.8   9.0   9.3   8.0   8.4properties Average particle diameter D50/nm 95  99  109  108  102 Initial viscosity (mPa · s)  17.8  18.5   2.3  12.2   7.7 Opticaldensity Measured value   0.92   0.98   0.87   0.90   0.87 Improvementrate 106% 113% (Reference) 111% 107% Determination G G — G G RubfastnessG G N G G Ink jet adaptability M M G G G Comparative Example ExampleExample Example Example Aqueous magenta ink (Type 2) 141 142 143 144 31Dispersion method (US: ultrasonic dispersion method) US US US US USComposition Magenta pigment Product name FASTOGEN FASTOGEN FASTOGENFASTOGEN FASTOGEN Super Super Super Super Super Magenta RY Magenta RYMagenta RY Magenta RY Magenta RY (parts) (solid content) 4 4 4 4 4Anionic group- Name/Product name UR-1 UR-1 UR-1 UR-1 UR-1 containingorganic (parts) (solid content)   1.2   1.2   1.2   1.2   1.2 polymercompound Name/Product name DN-800H DN-10L CMC DN-100L — 1390 (parts)(solid content)   0.15   0.1   0.2   0.15 — Bio-nanofiber Product nameCHI-NF CHI-NF CHI-NF CHI-NF — (abbreviation) (parts) (solid content)  0.15   0.15   0.1   0.4 — 2-Pyrrolidone (parts) 8 8 8 8 8 Triethyleneglycol 8 8 8 8 8 Glycerin (parts) 3 3 3 3 3 Triethylene glycol (parts) 44 4 4 4 Surfynol 440 (parts)   0.5   0.5   0.5   0.5   0.5 Pure waterBalance Balance Balance Balance Balance Total (parts) 100  100  100 100  100  Physical pH   8.1   8.5   7.4   8.4   7.9 properties Averageparticle diameter D50/nm 107  101  102  108  110  Initial viscosity (mPa· s)   9.3 9   7.8  18.2   2.9 Optical density Measured value   0.87  0.88   0.85   0.90   0.81 Improvement rate 107% 109% 105% 111%(Reference) Determination G G G G — Rubfastness G G G G N Ink jetadaptability G G G M G

TABLE 24 Production Example 7 PLM Example Example Example ExampleAqueous magenta ink (Type 2) Dispersion 145 146 147 148 Dispersionmethod (US: ultrasonic dispersion method PLM PLM PLM PLM PLM PLM:kneading method) Composition Magenta pigment Product name FASTOGENFASTOGEN FASTOGEN FASTOGEN FASTOGEN Super Super Super Super SuperMagenta RY Magenta RY Magenta RY Magenta RY Magenta RY (parts) (solidcontent) 8 4 4 4 4 Anionic group- Name/Product name Resin A Resin AResin A Resin A Resin A containing organic (parts) (solid content) 1.60.8 0.8 0.8 0.8 polymer compound Name/Product name — — — CMC — 1390(parts) (solid content) — — — 0.1 — Bio-nanofiber Product name CEL-KYCEL-KY CEL-KY CEL-KY CHI-NF (abbreviation) (parts) (solid content) 0.20.1 0.2 0.1 0.15 2-Pyrrolidone (parts) — 8 8 8 8 Triethylene glycol — 88 8 8 Glycerin (parts) — 3 3 3 3 Triethylene glycol (parts) 5.4 2.7 2.72.7 2.7 Surfynol 440 (parts) — 0.5 0.5 0.5 0.5 Pure water BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100Physical pH 10.3 9.2 9.2 9.2 8.8 properties Average particle diameterD50/nm 101 101 104 103 96 Initial viscosity (mPa · s) — 3.8 8.8 18.916.1 Optical density Measured value — 0.88 0.89 0.92 0.88 Improvementrate — 104% 105% 108% 104% Determination — G G G G Rubfastness — G G G GInk jet adaptability — G G G M Comparative Comparative Example ExampleExample Example Example Aqueous magenta ink (Type 2) 149 150 151 32 33Dispersion method (US: ultrasonic dispersion method PLM PLM PLM PLM PLMPLM: kneading method) Composition Magenta pigment Product name FASTOGENFASTOGEN FASTOGEN FASTOGEN FASTOGEN Super Super Super Super SuperMagenta RY Magenta RY Magenta RY Magenta RY Magenta RY (parts) (solidcontent) 4 4 4 4 4 Anionic group- Name/Product name Resin A Resin AResin A Resin A Resin A containing organic (parts) (solid content) 0.80.8 0.8 0.8 0.8 polymer compound Name/Product name DN-800H DN-100L CMCCMC — 1390 1390 (parts) (solid content) 0.15 0.15 0.1 0.1 —Bio-nanofiber Product name CHI-NF CHI-NF CHI-NF — — (abbreviation)(parts) (solid content) 0.1 0.2 0.15 — — 2-Pyrrolidone (parts) 8 8 8 8 8Triethylene glycol 8 8 8 8 8 Glycerin (parts) 3 3 3 3 3 Triethyleneglycol (parts) 2.7 2.7 2.7 2.7 2.7 Surfynol 440 (parts) 05 0.5 0.5 0.50.5 Pure water Balance Balance Balance Balance Balance Total (parts) 100100 100 100 100 Physical pH 9.2 9.3 9.0 9.2 9.2 properties Averageparticle diameter D50/nm 92 93 96 106 106 Initial viscosity (mPa · s)9.8 11.3 8.8 9.9 2.6 Optical density Measured value 0.88 0.91 0.90 0.860.85 Improvement rate 104% 107% 106% 101% (Reference) Determination G GG N — Rubfastness G G G N N Ink jet adaptability G M G G G

TABLE 25 Comparative Comparative Comparative Example Example ExampleExample Example Example Example Aqueous magenta ink (Type 2) 152 153 154155 34 35 36 Dispersion method (US: ultrasonic dispersion method Self-Self- Self- Self- Self- Self- Self- PLM: kneading method) dispersiondispersion dispersion dispersion dispersion dispersion dispersion typetype type type type type type Composition Magenta pigment Product nameCAB-O- CAB-O- CAB-O- CAB-O- CAB-O- CAB-O- CAB-O- JET JET JET JET JET JETJET 465M 465M 465M 465M 465M 465M 465M (parts) (solid content) 4 4 4 4 44 4 Anionic group- Name/Product name — — — — — — — containing organic(parts) (solid content) — — — — — — — polymer compound Name/Product nameCMC DN-800H CMC DN-800H — CMC — 1390 1390 1390 (parts) (solid content)0.2 0.2 0.2 0.2 — 0.2 — Bio-nanofiber Product name CEL-NF CEL-NF CEL-KYCEL-KY CEL-KY — — (abbreviation) (parts) (solid content) 0.2 0.2 0.2 0.20.5 — — 2-Pyrrolidone (parts) 8 8 8 8 8 8 8 Triethylene glycol 8 8 8 8 88 8 Glycerin (parts) 3 3 3 3 3 3 3 Triethylene glycol (parts) 1 1 1 1 11 1 Surfynol 440 (parts) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Pure water BalanceBalance Balance Balance Balance Balance Balance Total (parts) 100 100100 100 100 100 100 Physical pH 8.7 8.5 8.9 8.9 9.1 9.0 8.9 propertiesAverage particle diameter D50/nm 78 73 79 75 98 86 77 Initial viscosity(mPa · s) 13 9.3 11.5 8.8 298 6.9 2 Optical density Measured value 0.990.96 0.88 0.87 1.34 0.84 0.82 Improvement rate 121% 117% 107% 106% 163%102% (Reference) Determination G G G G G N — Rubfastness G G G G G N NInk jet adaptability G G G G N G G

TABLE 26 Production Example 4 US Example Example Example Example Aqueousyellow ink (Type 1) Dispersion 156 157 158 159 Dispersion method (US:ultrasonic dispersion method US US US US US PLM: kneading method)Composition Yellow pigment Product name Fast Yellow Fast Yellow FastYellow Fast Yellow Fast Yellow 7413 7413 7413 7413 7413 (parts) (solidcontent) 8 6 6 6 6 Anionic group- Name/Product name SA-1 SA-1 SA-1 SA-1SA-1 containing organic (parts) (solid content) 1.6 1.2 1.2 1.2 1.2polymer compound Name/Product name — — — CMC DN-800H 1390 (parts) (solidcontent) — — — 0.15 0.3 Bio-nanofiber Product name CEL-NF CEL-NF CEL-KYCEL-NF CEL-NF (abbreviation) (parts) (solid content) 0.4 0.3 0.3 0.150.3 Triethylene glycol (parts) 8 6 6 6 6 Pure water Balance BalanceBalance Balance Balance Total (parts) 100 100 100 100 100 Physical pH9.9 9.9 9.8 9.8 9.5 properties Average particle diameter D50/nm 99 99 87104 102 Initial viscosity (mPa · s) — 17.7 30.1 51.1 72.2 Opticaldensity Measured value — 1.30 1.22 1.36 1.34 Improvement rate — 111%104% 116% 114% Determination — G G G G Rubfastness — G G G G ComparativeExample Example Example Example Example Aqueous yellow ink (Type 1) 160161 167 163 37 Dispersion method (US: ultrasonic dispersion method US USUS US US PLM: kneading method) Composition Yellow pigment Product nameFast Yellow Fast Yellow Fast Yellow Fast Yellow Fast Yellow 7413 74137413 7413 7413 (parts) (solid content) 6 6 6 6 6 Anionic group-Name/Product name SA-1 SA-1 SA-1 SA-1 SA-1 containing organic (parts)(solid content) 1.2 1.2 1.2 1.2 1.2 polymer compound Name/Product name —— DN-800H DN-800H — (parts) (solid content) — — 0.15 0.3 — Bio-nanofiberProduct name CHI-NF CHI-NF CHI-NF CHI-NF — (abbreviation) (parts) (solidcontent) 0.075 0.225 0.375 0.45 — Triethylene glycol (parts) 6 6 6 6 6Pure water Balance Balance Balance Balance Balance Total (parts) 100 100100 100 100 Physical pH 9.6 10.0 9.6 9.8 9.5 properties Average particlediameter D50/nm 96 102 104 102 90 Initial viscosity (mPa · s) 3.4 5.114.2 28.9 1.5 Optical density Measured value 1.21 1.29 1.35 1.33 1.17Improvement rate 103% 110% 115% 113% (Reference) Determination G G G G —Rubfastness G G G G N

TABLE 27 Production Example 8 Comparative PLM Example Example ExampleExample Example Example Aqueous yellow ink (Type 1) Dispersion 164 165166 167 168 38 Dispersion method (US: ultrasonic dispersion method PLMPLM PLM PLM PLM PLM PLM PLM: kneading method) Composition Yellow pigmentProduct name Fast Fast Fast Yellow Fast Fast Yellow Fast Fast YellowYellow Yellow 7413 Yellow 7413 Yellow 7413 7413 7413 7413 7413 (parts)(solid content) 8 6 6 6 6 6 6 Anionic group- Name/Product name Resin AResin A Resin A Resin A Resin A Resin A Resin A containing organic(parts) (solid content) 2.4 1.8 1.8 1.8 1.8 1.8 1.8 polymer compoundName/Product name — — — CMC — DN-800H — 1390 (parts) (solid content) — —— 0.15 — 0.225 — Bio-nanofiber Product name CHI-NF CHI-NF CEL-KY CEL-KYCHI-NF CHI-NF — (abbreviation) (parts) (solid content) 0.1 0.075 0.150.15 0.225 0.6 — Triethylene glycol (parts) 4.4 3.3 3.3 3.3 3.3 3.3 3.3Pure water Balance Balance Balance Balance Balance Balance Balance Total(parts) 100 100 100 100 100 100 100 Physical pH 10.1 10.1 10.2 10.1 10.110.1 10.1 properties Average particle diameter D50/nm 86 86 62 73 87 8976 Initial viscosity (mPa · s) — 3.5 149.1 31.2 6.2 23.9 1.6 Opticaldensity Measured value — 1.08 1.10 1.15 1.20 1.22 1.03 Improvement rate— 105% 106% 111% 116% 118% (Reference) Determination — G G G G G —Rubfastness — G G G G G N

TABLE 28 Comparative Comparative Comparative Example Example ExampleExample Example Example Example Aqueous yellow ink (Type 1) 169 170 171172 39 40 41 Dispersion method (US: ultrasonic dispersion method Self-Self- Self- Self- Self- Self- Self- PLM: kneading method) dispersiondispersion dispersion dispersion dispersion dispersion dispersion typetype type type type type type Composition Yellow pigment Product nameCAB-O- CAB-O- CAB-O- CAB-O- CAB-O-JET CAB-O-JET CAB-O-JET JET JET JETJET 470Y 470Y 470Y 470Y 470Y 470Y 470Y (parts) (solid content) 6 6 6 6 66 6 Anionic group- Name/Product name — — — — — — — containing organic(parts) (solid content) — — — — — — — polymer compound Name/Product nameCMC DN-800H CMC DN-800H CMC — — 1390 1390 1390 (parts) (solid content)0.3 0.3 0.3 0.3 0.3 — — Bio-nanofiber Product name CEL-NF CEL-NF CEL-KYCEL-KY — CEL-NF — (abbreviation) (parts) (solid content) 0.3 0.3 0.3 0.3— 0.75 — Triethylene glycol (parts) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Purewater Balance Balance Balance Balance Balance Balance Balance Total(parts) 100 100 100 100 100 100 100 Physical pH 8.9 8.8 9.0 8.9 9.9 10.19.0 properties Average particle diameter D50/nm 132 137 126 123 80 189113 Initial viscosity (mPa · s) 14.2 9.3 11.8 8.1 3.9 611 1.2 Opticaldensity Measured value 1.22 1.19 1.10 1.07 1.05 1.58 1.03 Improvementrate 118% 116% 107% 105% 102% 153% (Reference) Determination G G G G N G— Rubfastness G G G G N N N

TABLE 29 Production Example 4 US Example Example Example Example ExampleAqueous yellow ink (Type 2) Dispersion 173 174 175 176 177 Dispersionmethod (US: ultrasonic dispersion US US US US US US method PLM: kneadingmethod) Composition Yellow Product name Fast Yellow Fast Yellow FastYellow Fast Yellow Fast Yellow Fast Yellow pigment 7413 7413 7413 74137413 7413 (parts) (solid content) 8 4 4 4 4 4 Anionic Name/Product nameSA-1 SA-1 SA-1 SA-1 SA-1 SA-1 group- (parts) (solid content) 1.6 0.8 0.80.8 0.8 0.8 containing Name/Product name — — — — CMC DN-800H organic1390 polymer (parts) (solid content) — — — — 0.1 0.1 compound Bio-Product name CEL-NF CEL-NF CEL-KY CEL-KY CEL-KY CEL-KY nanofiber(abbreviation) (parts) (solid content) 0.4 0.2 0.2 0.1 0.1 0.12-Pyrrolidone (parts) — 8 8 8 8 8 Triethylene glycol — 8 8 8 8 8Glycerin (parts) — 3 3 3 3 3 Triethylene glycol (parts) 8 4 4 4 4 4Surfynol 440 (parts) — 0.5 0.5 0.5 0.5 0.5 Pure water Balance BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100 100Physical pH 9.9 9.0 8.9 9.2 8.9 8.6 properties Average particle diameterD50/nm 99 106 94 110 112 120 Initial viscosity (mPa · s) — 2.7 18.7 10.819.5 17.6 Optical Measured value — 1.07 1.01 1.00 1.03 1.04 densityImprovement rate — 110% 104% 103% 106% 107% Determination — G G G G GRubfastness — G G G G G Ink jet adaptability — G M G M M Example ExampleExample Example Example Example Aqueous yellow ink (Type 2) 178 179 180181 182 183 Dispersion method (US: ultrasonic dispersion US US US US USUS method PLM: kneading method) Composition Yellow Product name FastYellow Fast Yellow Fast Yellow Fast Yellow Fast Yellow Fast Yellowpigment 7413 7413 7413 7413 7413 7413 (parts) (solid content) 4 4 4 4 44 Anionic Name/Product name SA-1 SA-1 SA-1 SA-1 SA-1 SA-1 group- (parts)(solid content) 0.8 0.8 0.8 0.8 0.8 0.8 containing Name/Product nameDN-10L CMC DN-800H DN-10L — — organic 1390 polymer (parts) (solidcontent) 0.1 0.2 0.2 0.2 — — compound Bio- Product name CEL-KY CEL-NFCEL-NF CEL-NF CHI-NF CHI-NF nanofiber (abbreviation) (parts) (solidcontent) 0.1 0.2 0.7 0.2 0.05 0.15 2-Pyrrolidone (parts) 8 8 8 8 8 8Triethylene glycol 8 8 8 8 8 8 Glycerin (parts) 3 3 3 3 3 3 Triethyleneglycol (parts) 4 4 4 4 4 4 Surfynol 440 (parts) 0.5 0.5 0.5 0.5 0.5 0.5Pure water Balance Balance Balance Balance Balance Balance Total (parts)100 100 100 100 100 100 Physical pH 8.8 8.8 8.6 8.8 8.7 9.1 propertiesAverage particle diameter D50/nm 119 109 110 133 103 110 Initialviscosity (mPa · s) 11.2 5.4 2.7 19.9 3.6 11.8 Optical Measured value1.05 1.10 1.10 1.08 1.00 1.06 density Improvement rate 108% 113% 113%111% 103% 109% Determination G G G G G G Rubfastness G G G G G G Ink jetadaptability G G G M G G

TABLE 30 Comparative Example Example Example Example Example ExampleExample Aqueous yellow ink (Type 2) 184 185 186 187 188 189 42Dispersion method (US: ultrasonic dispersion method US US US US US US USPLM: kneading method) Composition Yellow pigment Product name Fast FastFast Fast Fast Fast Fast Yellow Yellow Yellow Yellow Yellow YellowYellow 7413 7413 7413 7413 7413 7413 7413 (parts) (solid content) 4 4 44 4 4 4 Anionic group-containing Name/Product name SA-1 SA-1 SA-1 SA-1SA-1 SA-1 SA-1 organic polymer (parts) (solid content) 0.8 0.8 0.8 0.80.8 0.8 0.8 compound Name/Product name DN-800H CMC DN-100L DN-10LDN-800H DN-800H — 1390 (parts) (solid content) 0.1 0.1 0.15 0.2 0.1 0.2— Bio-nanofiber Product name CHI-NF CHI-NF CHI-NF CHI-NF CHI-NF CHI-NF —(abbreviation) (parts) (solid content) 0.15 0.15 0.15 0.1 0.25 0.3 —2-Pyrrolidone (parts) 8 8 8 8 8 8 8 Triethylene glycol 8 8 8 8 8 8 8Glycerin (parts) 3 3 3 3 3 3 3 Triethylene glycol (parts) 4 4 4 4 4 4 4Surfynol 440 (parts) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Pure water BalanceBalance Balance Balance Balance Balance Total (parts) 100 100 100 100100 100 100 Physical pH 8.9 9.0 8.7 8.6 8.7 8.9 8.6 properties Averageparticle diameter D50/nm 111 113 108 106 101 110 97 Initial viscosity(mPa · s) 5.5 18.9 5.1 11.2 19.8 12.5 2.8 Optical density Measured value1.01 1.03 1.03 1.03 1.09 1.05 0.97 Improvement rate 104% 106% 106% 106%112% 108% (Reference) Determination G G G G G G — Rubfastness G G G G GG G Ink jet adaptability G M G G M G G

TABLE 31 Production Example 8 PLM Example Example Example ExampleExample Aqueous yellow ink (Type 2) Dispersion 190 191 192 193 194Dispersion method (US: ultrasonic dispersion method PLM PLM PLM PLM PLMPLM PLM: kneading method) Composition Yellow pigment Product name FastFast Fast Fast Fast Fast Yellow Yellow Yellow Yellow Yellow Yellow 74137413 7413 7413 7413 7413 (parts) (solid content) 8 4 4 4 4 4 Anionicgroup- Name/Product name Resin A Resin A Resin A Resin A Resin A Resin Acontaining organic (parts) (solid content) 2.4 1.2 1.2 1.2 1.2 1.2polymer compound Name/Product name — — — — CMC — 1390 (parts) (solidcontent) — — — — 0.1 — Bio-nanofiber Product name CHI-NF CHI-NF CEL-KYCEL-KY CEL-KY CHI-NF (abbreviation) (parts) (solid content) 0.1 0.05 0.20.1 0.1 0.15 2-Pyrrolidone (parts) — 8 8 8 8 8 Triethylene glycol — 8 88 8 8 Glycerin (parts) — 3 3 3 3 3 Triethylene glycol (parts) 4.4 2.22.2 2.2 2.2 2.2 Surfynol 440 (parts) — 0.5 0.5 0.5 0.5 0.5 Pure waterBalance Balance Balance Balance Balance Total (parts) 100 100 100 100100 100 Physical pH 10.1 9.2 9.3 9.3 9.2 9.2 properties Average particlediameter D50/nm 86 82 78 67 79 82 Initial viscosity (mPa · s) — 3.1 15.64.3 19.6 16.1 Optical density Measured value — 0.90 0.92 0.91 0.95 0.99Improvement rate — 105% 107% 106% 110% 115% Determination — G G G G GRubfastness — G G G G G Ink jet adaptability — G G G M M Example ExampleExample Example Example Example Aqueous yellow ink (Type 2) 195 196 197198 199 200 Dispersion method (US: ultrasonic dispersion method PLM PLMPLM PLM PLM PLM PLM: kneading method) Composition Yellow pigment Productname Fast Fast Fast Fast Fast Fast Yellow Yellow Yellow Yellow YellowYellow 7413 7413 7413 7413 7413 7413 (parts) (solid content) 4 4 4 4 4 4Anionic group- Name/Product name Resin A Resin A Resin A Resin A Resin AResin A containing organic (parts) (solid content) 1.2 1.2 1.2 1.2 1.21.2 polymer compound Name/Product name DN-800H CMC DN-100L DN-10LDN-800H DN-800H 1390 (parts) (solid content) 0.15 0.1 0.15 0.2 0.1 0.15Bio-nanofiber Product name CHI-NF CHI-NF CHI-NF CHI-NF CHI-NF CHI-NF(abbreviation) (parts) (solid content) 0.15 0.15 0.15 0.1 0.25 0.42-Pyrrolidone (parts) 8 8 8 8 8 8 Triethylene glycol 8 8 8 8 8 8Glycerin (parts) 3 3 3 3 3 3 Triethylene glycol (parts) 2.2 2.2 2.2 2.22.2 2.2 Surfynol 440 (parts) 0.5 0.5 0.5 0.5 0.5 0.5 Pure water BalanceBalance Balance Balance Balance Total (parts) 100 100 100 100 100 100Physical pH 9.2 9.2 9.2 9.2 9.2 9.2 properties Average particle diameterD50/nm 82 82 82 82 82 85 Initial viscosity (mPa · s) 8.4 10.9 8.8 7.29.9 17.9 Optical density Measured value 0.91 0.92 0.96 0.94 0.99 1.01Improvement rate 106% 107% 112% 109% 115% 117% Determination G G G G G GRubfastness G G G G G G Ink jet adaptability G G G G G M

TABLE 32 Comparative Comparative Example Example Example Example ExampleAqueous yellow ink (Type 2) 43 44 201 202 203 Dispersion method (US:ultrasonic dispersion method PLM PLM Self-dispersion Self-dispersionSelf-dispersion PLM: kneading method) type type type Composition Yellowpigment Product name Fast Yellow Fast Yellow CAB-O-JET CAB-O-JETCAB-O-JET 7413 7413 470Y 470Y 470Y (parts) (solid content) 4 4 4 4 4Anionic group- Name/Product name Resin A Resin A — — — containingorganic (parts) (solid content) 1.2 1.2 — — — polymer compoundName/Product name CMC — CMC DN-800H CMC 1390 1390 1390 (parts) (solidcontent) 0.1 — 0.2 0.2 0.2 Bio-nanofiber Product name — — CEL-NF CEL-NFCEL-KY (abbreviation) (parts) (solid content) — — 0.2 0.2 0.22-Pyrrolidone (parts) 8 8 8 8 8 Triethylene glycol 8 8 8 8 8 Glycerin(parts) 3 3 3 3 3 Triethylene glycol (parts) 2.2 2.2 1 1 1 Surfynol 440(parts) 0.5 0.5 0.5 0.5 0.5 Pure water Total (parts) 100 100 100 100 100Physical pH 9.2 9.2 8.1 8.0 8.2 properties Average particle diameterD50/nm 82 82 142 147 135 Initial viscosity (mPa · s) 10.2 2.7 13.2 11.210.9 Optical density Measured value 0.87 0.86 1.09 1.07 0.99 Improvementrate 101% (Reference) 117% 118% 109% Determination N — G G G RubfastnessN N G G G Ink jet adaptability G G G G G Comparative ComparativeComparative Example Example Example Example Aqueous yellow ink (Type 2)204 45 46 47 Dispersion method (US: ultrasonic dispersion methodSelf-dispersion Self-dispersion Self-dispersion Self-dispersion PLM:kneading method) type type type type Composition Yellow pigment Productname CAB-O-JET CAB-O-JET CAB-O-JET CAB-O-JET 470Y 470Y 470Y 470Y (parts)(solid content) 4 4 4 4 Anionic group- Name/Product name — — — —containing organic (parts) (solid content) — — — — polymer compoundName/Product name DN-800H — DN-800H — (parts) (solid content) 0.2 — 0.2— Bio-nanofiber Product name CEL-KY CEL-NF — — (abbreviation) (parts)(solid content) 0.2 0.5 — — 2-Pyrrolidone (parts) 8 8 8 8 Triethyleneglycol 8 8 8 8 Glycerin (parts) 3 3 3 3 Triethylene glycol (parts) 1 1 11 Surfynol 440 (parts) 0.5 0.5 0.5 0.5 Pure water Total (parts) 100 100100 100 Physical pH 8.1 9.2 8.7 8.2 properties Average particle diameterD50/nm 132 203 88 121 Initial viscosity (mPa · s) 9.2 456.0 5.5 2.0Optical density Measured value 0.97 1.40 0.94 0.93 Improvement rate 107%154% 103% ( 

 ) Determination G G N — Rubfastness G G N N Ink jet adaptability G N GG

The results indicate that an aqueous ink of each color using an aqueouspigment dispersion containing an anionic group-containing organicpolymer compound and bio-nanofibers having an average diameter of 1 nmor more and 100 nm or less and an aspect ratio of 100 or more isexcellent in optical density, rubfastness, etc. of resultant images.

The invention claimed is:
 1. A method of performing printing on arecording material, the method comprising: applying to the recordingmaterial an aqueous ink composition comprising a pigment, an anionicgroup-containing organic polymer compound, and unmodified bio-nanofibershaving an average diameter of 1 nm or more and 50 nm or less and anaspect ratio of 100 or more; and drying the aqueous ink composition onthe recording material.
 2. The method according to claim 1, wherein theaspect ratio of the unmodified bio-nanofibers is 2000 or less.
 3. Themethod according to claim 1, which said printing is ink jet printing.